Despite Iran's runaway nuclear program, North Korea's atomic assistance to Syria, and robust ballistic missile production and testing by Russia and China, a missile defense system for protecting the homeland and U.S. interests overseas remains a controversial idea in some corners. It should not be. The security challenge arising from the proliferation of ballistic missiles and the dangerous payloads they might carry, including weapons of mass destruction (WMD) like nuclear arms, is a threat that -- in fact -- may be growing.

While the Bush administration has taken significant steps to develop sea- and land-based missile defense systems, the next White House and Congress should continue supporting missile defense programs to enhance our national security. Indeed, just this summer, the Washington Post broke a story claiming the international nuclear smuggling ring once run by the prodigious Pakistani proliferator A.Q. Khan had also managed to acquire the blueprints for an "advanced nuclear weapon."

Owned by three Swiss members of Khan's international cabal, a laptop containing 1,000 gigabytes of data (roughly equivalent to the information contained in a local library) on designs and engineering for nuclear weapons was discovered by investigators. Regrettably, according to the story, the United Nations' International Atomic Energy Agency (IAEA) believes the nuclear weapons designs found on the laptop could be mated -- in theory -- to the ballistic missiles used by "more than a dozen developing countries."

In fact, the IAEA, which reportedly verified the destruction of the data by Swiss authorities, cannot guarantee the nuclear warhead designs were not shared with others, according to a report by David Albright, a weapons expert who has been investigating the Khan network. While North Korea, Iran and Libya -- the three states with which Khan had the most intimate contact -- are the most likely recipients of the Pakistani's atomic assistance, there may be others who received this nuclear know-how as well, although some experts view the report as alarmist. (Not surprisingly, Khan, who has been under house arrest in Pakistan since 2004, denied that he was involved in any way in proliferating nuclear weapons designs. Of course, others in his nuclear network may have done so.)

With Israel's strike on a suspected Syrian nuclear site in September 2007 and news of nuclear power programs popping up across the Middle East (which may be hedging against Iran's nuclear efforts), this sort of dire speculation about possible proliferation makes security experts increasingly nervous. Indeed, the ballistic missile and nuclear proliferation trend is not positive. Ten years ago, there were only six nuclear-weapons states. Today there are nine members of the once-exclusive nuclear-weapons club, with Iran perhaps knocking at the door. Twenty-five years ago, nine countries had ballistic missiles. Today there are 28 countries with ballistic missile arsenals of varying capability.

Iranian Intrigue

Among present proliferation problems, Iran may be the most troubling to American security analysts, especially considering its longstanding enmity toward the United States, sponsorship of terrorism, involvement in Iraq and Afghanistan, and regional great-power ambitions.

Tehran, naturally, insists its burgeoning nuclear program is for little more than peaceful power generation, designed to augment Iran's already significant oil and natural gas reserves. (Iran has the world's third largest oil and second largest natural gas reserves.) But like a sledgehammer, new intelligence continues to blast away at Iran's rock-like insistence that its nuclear program is purely peaceful and not a weapons effort as many in the region and beyond increasingly believe.

The most serious blow comes out of the United Nations' nuclear watchdog in Vienna, the IAEA, which drafted and released a troubling nine-page report in late May casting serious doubt on Iran's claims to a purported pacifist power program. In a dramatic change, based on new multi-source, multilateral intelligence received over time from a number of its member states, the IAEA has shifted its position from being unable to prove Iran has a nuclear weapons program to being unable to prove Iran does not have one. (Indeed, in late June, IAEA chief Mohamed El Baradei commented on Arab television that Iran could build a nuclear weapon in six months to a year if it decided to do so, considering its current centrifuge capacity and the quantity of processed uranium it already has on hand.)

Ten years ago, there were only six nuclear weapons states. Today there are nine, with Iran perhaps aiming to be the tenth.

Based on 18 hard-copy and electronic documents, the nuclear-monitoring agency expressed concerns about the increasingly questionable nature of Iran's nuclear program, especially its possible military dimensions, which would violate Iran's Nuclear Non-Proliferation Treaty (NPT) commitments. (The NPT allows signatories to pursue nuclear programs for scientific or power purposes, but not military ends, which include weapons production. All activities must be declared to the IAEA Of note, not all states have signed the NPT, most notably India, Pakistan, and Israel; North Korea withdrew.)

In its first formal assessment of Iran's nuclear efforts since February, the IAEA states in the most "diplomatic" of terms: "The agency [IAEA] is of the view that Iran may have additional information, in particular on high explosives testing and missile-related activities, which could shed more light on the nature of these alleged studies and which Iran should share with the agency."

The IAEA considers these unanswered questions on Iran's nuclear work "a matter of serious concern" because the existence of this sort of activity might indicate Tehran is secretly developing a nuclear weapon, contrary to Iran's repeated public protestations. Moreover, the report states, "Iran has not provided the agency with all the information, access to documents and access to individuals necessary to supports Iran's statements," despite the new intelligence, which is "detailed in content, and appears to be generally consistent."

The first charge is that Iran is suspected of conducting high-explosives testing. This includes work with exploding bridge wire (EBW) detonators and a detonator firing unit, which could be used for triggering a nuclear weapon; 500ebw detonators were tested, according to the IAEA

In addition, a five-page document describes experiments for a "complex multipoint initiation system" to "detonate a substantial amount of high explosive in hemispherical geometry" that could be employed in an implosion-type nuclear device. Tehran is further accused of developing plans for underground explosives testing, which could be utilized for detonating a nuclear weapon similar to the testing done by North Korea in October 2006. The documents also include a technical diagram for a "400m deep shaft located 10km from a firing control point," showing "the placement of various electronic systems such as a control unit and a high-voltage power generator."

It seems military-related institutions are involved in procurement activities for Iran's "peaceful" nuclear power program.

There is also a mysterious piece of information the IAEA report calls the "uranium metal document," which is related to the "actual design or manufacture by Iran of nuclear material components of a nuclear weapon." The document allegedly describes procedures for machining highly enriched uranium metal into a hemispherical shape, key to producing the rounded "pits" used in modern implosion-type nuclear weapon warheads. Strikingly, the report notes that "Pakistan has confirmed, in response to the Agency's request, that an identical document exists in Pakistan" to the one found in Iran -- possibly showing connections to Pakistan's nuclear weapons program.

Another IAEA concern is work on a new ballistic missile warhead, known as "Project 111," for Iran's medium-range ballistic missile, the Shahab-3, which can reach all of the Middle East as well as parts of southern Europe. According to six technical documents in the IAEA's possession, Iran appears to have been involved in the redesign of the payload chamber of the current "Shahab-3 missile re-entry vehicle to accommodate a nuclear warhead."

The IAEA report also questions the Iranian military's apparent involvement in Tehran's civilian nuclear efforts. It seems military-related institutions are involved in suspicious procurement activities for Iran's ostensibly "peaceful" nuclear power program. There are also concerns, according to the report, about an unexplained letter published by the chairman of Iran's high-ranking Expediency Council in September, which makes "reference to possible acquisition of nuclear weapons."

If this is not unnerving enough, it gets worse. The report notes that Iran continues uranium enrichment, the proverbial "long-pole in the tent" in producing a nuclear weapon -- at least in comparison with developing a delivery platform or warhead. As the American IAEA representative, Ambassador Gregory Schulte, told the press in May: "At the same time that Iran is stonewalling its [IAEA] inspectors, it's moving forward in developing its enrichment capability in violation of [UN] Security Council resolutions."

Iran's uranium enrichment plant at Natanz is already using at least 3,500 centrifuges. Theoretically, if operating efficiently, this line could produce enough weapons-grade fissile material to build one bomb in the time indicated by El Baradei. (The uranium enrichment process can produce fuel for a nuclear power reactor or fissile material for a nuclear weapon. To date, Iran has publicly stated enrichment rates of over 4 percent, suitable for reactor fuel if produced in sufficient quantities; weapons-grade uranium is usually enriched to above 90 percent.)

Some experts think Iran could have as many as 6,000 centrifuges online, spinning at supersonic speed in the near future, turning uranium hexafluoride gas (uf6) into some level of enriched uranium for reactors, weapons or both. Tehran has steadfastly insisted that it has the right to enrich uranium for nuclear reactor fuel as stipulated under the terms of the NPT (ironically, Iran violated the NPT by failing to declare its nuclear program to the IAEA for some 20 years.)

Iran, with Russian assistance, is continuing construction of its first nuclear reactor at Bushehr.

The new IAEA report also notes the previously undisclosed development of a new generation of centrifuge. The "IR-3" (for third generation Iranian) centrifuge improves upon previous models based on the less efficient Pakistani design, procured from Khan's network. Moreover, agency inspectors raise concerns about the fact that "substantial parts of the centrifuge components were manufactured in the workshops of the [Iranian] Defense Industries Organization," hoisting a red flag about the blurring of the lines between Tehran's civilian and a possible military program.

The bottom line concern here, besides the fact that Iran did not declare this new equipment (and capability) to the IAEA as required, is that the new, more efficient centrifuges will allow Iran to produce more enriched uranium -- for reactors or bombs -- more quickly. Iran, with Russian assistance, is also continuing construction of its first nuclear reactor at Bushehr. A good deal of the reactor's fuel is already in place, having been shipped in from Russia beginning last December. (Unfortunately, Russian support at the UN Security Council for slowing Iran's nuclear program through the imposition of economic sanctions is likely to diminish following this summer's action in Georgia.) The IAEA is also monitoring construction of an Iranian nuclear research reactor, which experts are concerned could be used for experimentation on reprocessing spent nuclear reactor fuel into fissile material (e.g., plutonium) for use in nuclear weapons.

Interestingly, in all of this Iran does not see an indictment of wrongdoing on its part. On the contrary, Tehran views the report as an exoneration of guilt. Iran's IAEA envoy, via the Iranian news service, called the report: "[a] vindication and reiteration of the peaceful nature of Iran's nuclear activities." In addition, Tehran officially said the IAEA documents "do not show any indication that the Islamic Republic of Iran has been working on a nuclear weapon," adding that many of the documents had been "forged" or "fabricated," especially since they were in an electronic format. In some cases, Iran did not quibble with the information, instead insisting that "the events and activities concerned involved civil or conventional military applications," such as the testing of detonators for use in the oil industry. While Iran has promised to address all concerns, many of these questions are likely to remain a mystery due to Iran's regular refusal to allow the IAEA access to procurement personnel and scientists or to open suspect sites to the agency's atomic sleuths.

The IAEA reports starkly call into question the intent of Iran's nuclear efforts, leaving Tehran's claims to a purely civilian nuclear power program increasingly in doubt. As a result, the IAEA has called upon Tehran to increase transparency by signing an "Additional Protocol," which would give agency inspectors access to any facility suspected of undeclared nuclear activity.

This is a fundamental requirement in a large country like Iran (four times the size of California), where sites are numerous and sometimes well-hidden -- even below ground. Verification of compliance, even under the best of conditions, is likely to be difficult. But old habits die hard. Tehran will likely continue to obfuscate and dissemble, preventing the IAEA from gaining a realistic assessment of the nature of Iran's nuclear program -- which unfortunately places time squarely on Tehran's side.

Islamic ICBM

Iran's interest and involvement in a nascent space program is not comforting either. While enriching uranium is a key capability in developing nuclear weapons, Iran may also be working on another important aspect of a military program: a long-range delivery system; that is, a new ballistic missile. Like its "civilian" nuclear efforts that remained undeclared for two decades, long-range ballistic missiles are likely being developed under cover of another supposed nonmilitary effort: Iran's space program. Indeed, Tehran's budding space work could lead to the development of an intercontinental ballistic missile (ICBM) capable of reaching all of Europe and the United States with a WMD payload.

For example, on February 5 Iranian President Mahmoud Ahmadinejad led the countdown for the launch of a ballistic missile described as a "space launch vehicle," or SLV, from a new space center inaugurated the same day. While there is controversy about the success of that day's test, Iran claims it was setting the stage for the future launch of the first Iranian-built satellite -- the Omid (Hope) -- which is expected to be ready for service by mid-2009. Undeterred, Iran conducted a second space-related missile launch this summer.

Of course, Iran has a lot of relatively benign reasons to want a space program. National pride in such an achievement might distract the restive populace from its social and economic suffering, helping to legitimize the increasingly unpopular regime. The program could also build prestige for the ambitious state: Iran would be the first Muslim state with a space-launch capability. Neighbors would be envious as Tehran propels itself toward leadership of the Middle East and the Islamic world.

It is also useful to be able to launch your own communications, intelligence or scientific satellites rather than relying on others to launch them for you. (Russia launched Iran's only other satellite into orbit back in October 2005.) Iran would surely argue that it needs to be self-reliant for space launches, just as it (self-servingly) insists it needs to be self-sufficient in enriching uranium to produce fuel for Bushehr despite Russian assistance.

Experts think a two-stage ballistic missile from Iran could reach all of Europe -- and America's East Coast.

There are other advantages. Satellites could enhance Iran's military might, relaying secure communications, gathering intelligence, providing early warning and targeting opposition forces, such as U.S. naval and air forces in the Persian Gulf. In addition, a space program, especially a space-launch capacity, is critical to developing an ICBM capability. Remember: Moscow's launch of its first satellite, Sputnik, in 1957 meant not only that the Russians had bested us scientifically, but that a Soviet ICBM capability was not far behind. Theoretically, if you can launch a ballistic missile that can place a satellite into Earth orbit, you have the scientific wherewithal to hit a target anywhere on Earth with a warhead, including a WMD.

Similarly, Iran's space efforts follow an unnerving proliferation pattern. In the late 1990s, North Korea also used a "civilian" space program to clandestinely manufacture and test a Taepo Dong ballistic missile with intercontinental potential. Fortunately, the 1998 multi-stage missile launch landed in the Western Pacific after overflying Japan, while North Korea oddly insisted the launch had successfully put a small satellite into orbit, transmitting patriotic songs back to eager listeners on the ground in impoverished North Korea.

Also striking, Iran's defense ministry plays a prominent role in the putative civilian space effort. The Islamic Revolutionary Guard Corps, which is close to Tehran's political leadership, manages Iran's Shahab medium-range ballistic missile program. Some experts believe the Shahab, which is based on the North Korean (medium-range) No Dong missile, could easily morph into an SLV/ICBM program. Indeed, the Taepo Dong is believed to be based on various No Dong rocketry configurations.

Fortunately, without a Manhattan Project-like effort, an Iranian ICBM is not just around the corner: Iran still needs a more energetic (i.e., multistage) missile to carry a nuclear-sized payload (1,000-2,000 pounds) to intercontinental ranges. Although Iran has not yet been totally successful in testing a multistage missile, experts estimate a two-stage ballistic missile from Iran could reach all of Europe -- as well as America's East Coast. A ballistic missile with three stages could range the whole of the United States.

The downside is that Iran could move forward with alacrity if it receives outside assistance on its space and/or missile program. The most likely candidates for that assistance are North Korea, Russia, or a Khan-like network of ballistic missile "guns for hire."

Despite mounting evidence to the contrary, Iran could in the end just be working on a space program -- not an ICBM program. But considering Tehran's record of nuclear denial and deception, it is hard to believe Iran's space program is not just more of the same. Equally troubling, in the view of many analysts, is that absent a political decision by Tehran to stay non-nuclear, it will be almost impossible to prevent Iran from a nuclear breakout, meaning that at some point in the future an Iranian ICBM may be capable of being mated with an Iranian nuclear warhead.

Korean Conundrum

From a threat perspective, unfortunately, there is not much good news out of North Korea, either, regarding its nuclear or ballistic missile programs. While the situation is perhaps not as volatile as Iran's, North Korea remains a cause of concern.

North Korea is already a confirmed nuclear weapons state, lighting off its first nuclear test in a subterranean event in October 2006 -- in another of its irascible "I will not be ignored" moments. Containing, much less rolling back, North Korea's nuclear program (beginning in the early years of the Clinton administration) has been a tough, frustrating slog. At times, it looked as if the nuclear standoff could lead to another Korean conflict.

Even today, despite North Korea's rhetoric and some actions to the contrary, there remains serious concern about Pyongyang's ultimate willingness to fully denuclearize, since its nuclear arsenal is a strong bargaining chip -- and a great equalizer against the strength of the U.S.-South Korean alliance. Complicating matters, North Korea is believed to have a clandestine, parallel uranium-based nuclear program in addition to its well-known plutonium-based program centered around its Russian-made nuclear reactor at Yongbyon.

While the United States has accused North Korea directly of having a uranium-based nuclear program, Pyongyang has been evasive, even contradictory, about the existence of this second nuclear program since Washington first confronted North Korean officials about it in the fall of 2002 in Pyongyang. (A major news outlet reported that traces of highly enriched uranium were found on some of the 18,000 pages of North Korean documents provided to the United States in June as part of a nuclear declaration. Some observers, however, believe this story is apocryphal.)

The multilateral effort to address North Korea's nuclear program has labored for several years under a Six-Party Talks process, which includes the United States, China, Russia, Japan, and North and South Korea, hosted by the Chinese in Beijing. The forum was unable to prevent North Korea from going nuclear, and has evolved from the six-member format into what are now essentially bilateral talks between Washington and Pyongyang, with frequent consultations with the other four players.

Though some progress has been made in capturing the nuclear reactor at Yongbyon, an important site for producing fissile material for weapons, the next steps in addressing North Korea's existing nuclear weapons capability and the uranium-based program remain an open question. (Of course, the issue of verification and compliance of any nuclear agreement with the ultra-secretive North Koreans has to weigh heavily on the mind of any Washington policymaker contemplating an effective, enduring settlement with Pyongyang.)

North Korea is still developing a long-range missile capability to reach out and touch the United States.

Making the future of the nuclear weapons issue more than a matter of regional importance is North Korea's ballistic missile prowess. In addition to the 1998 Taepo Dong launch, North Korea is still developing a long-range capability to reach out and touch the United States. In 2006, North Korea test-fired another Taepo Dong missile that malfunctioned approximately 40 seconds after launch, landing a few hundred miles west in the Sea of Japan. Naturally, once again, Pyongyang claimed a test of an SLV; once again, very few outside the Hermit Kingdom were swayed by the claim. While the exact capabilities of the Taepo Dong series of ballistic missile are unknown, mostly due to their largely-failed launches, it is believed the missile is capable of reaching well into the Pacific Ocean, including Hawaii, and possibly the West Coast of the United States. (The deployment of American missile defenses at Vandenberg Air Force Base in California and Fort Greeley in Alaska, totaling 24-30 ground-based interceptors, is meant to provide a rudimentary defense against the North Korean nuclear and ballistic missile threat.)

North Korea poses a threat to U.S. forces stationed in-theater with its single-stage No Dong missile. The No Dong, which serves as the rocketry building block for the Taepo Dong, can reach American bases and forces in Japan, which might be called upon in a Korean Peninsula contingency. On the peninsula, the 25,000 or so American troops also face a North Korean ballistic missile threat, consisting of several hundred short-range Scud-b/c tactical ballistic missiles capable of reaching targets in the South within minutes of launch. While there are still questions about the ability of Pyongyang to successfully mount a nuclear warhead capable of withstanding the great heat and pressure common to medium and long-range missile flight, the North Koreans likely can mate chemical and biological weapons to scuds.

Adding to the anxiety about North Korea's nuclear and ballistic missile capabilities are recent reports about Pyongyang's proliferation activities off the Korean Peninsula: North Korea may have been furtively assisting Syria with a nuclear program of its own. Last September, in a still-secretive raid, Israeli fighters leveled a suspected Syrian nuclear facility in the northern part of the country at al Kibar, which, as details dribbling out into the media have shown, may have been supported by North Korean technology and technicians.

While this sort of negative exposure is not good for Pyongyang's public image on the world stage, the destitute North Koreans are likely willing to work with any number of state actors on nuclear and ballistic missile matters if the price is right.

China Challenge

While not an avowed adversary of the United States, China is -- without question -- involved in an intense competition with America for power and influence in the Asia-Pacific region and, with little doubt, globally. Chinese great power ambitions are buttressed by a robust military modernization effort, which has been growing at a double-digit rate for over a decade now. Indeed, China now has the world's third largest defense budget, according to the Pentagon, growing at an average of 18 percent for the last two years alone. Moreover, according to some security analysts, China has the most active ballistic missile program in the world, most likely a reflection of the unresolved situation surrounding the longstanding political stand-off with China's cross-strait rival, Taiwan.

Since the end of the Chinese civil war in 1949, the PRC has considered Taiwan to be a province of the People's Republic. While progress on any form of political reconciliation has been lacking, China has not renounced the use of force in resolving Taiwan's political future. And while the United States does not have a legal obligation to defend Taiwan, under the 1979 Taiwan Relations Act, aggression against the island would be considered a serious threat to American interests as well as a violation of longstanding U.S. policy of promoting a peaceful, mutually agreeable resolution of the issue. Consequently, if the PRC were to move against Taiwan with force, it is widely believed in Washington policy circles that the United States would militarily oppose such a move, bringing U.S. and Chinese forces into direct military contact in the Western Pacific.

To deter Taiwanese movement toward independence or other acts China considers "hostile," the PRC has deployed vast numbers of df-11/15 (css-6/7) short-range ballistic missiles along the coast opposite Taiwan; Pentagon estimates run in the range of 1,000 to 1,100. Moreover, China is believed to be deploying roughly 100 new, highly accurate ballistic missiles a year to augment an already overwhelming force opposite Taiwan. Some have asserted that the number of new missiles may be pushed to 200 per year.

These missiles not only provide strong Chinese deterrent to unwanted Taiwanese political or military actions, but also could be used to great effect in a "bolt from the blue" scenario to decapitate Taiwan's political leadership or strike critical military targets such as ports, airfields, and air defenses. Apropos of what it considers outside interference in an internal matter, China does maintain limited medium-range, intermediate-range and ICBM forces for deterring, delaying or denying the threat of foreign military involvement in a Taiwan contingency, such as by the United States and Japan, as well as other potential military contingencies with the likes of Russia or India.

China has modernized its land-based strategic nuclear deterrent too, adding road-mobile, solid-fueled ICBMs to its arsenal, increasing its deterrent effect and survivability. A new concern is China's plans to put its nuclear deterrent to sea, equipping its Jin-class (Type 094) nuclear submarines with the new jl-2 missile with intercontinental range; a jl-2 was tested in late May. Of equal concern, beyond the growing capacity of China's ballistic missile force, is the continuing potential for witting -- or unwitting -- proliferation of WMD and ballistic missile technology or materials. While China's proliferation record has improved, concerns still exist about ties with North Korea and Iran.

Resurgent Russia

The Russian Federation, like China, is not an enemy of the United States, but it, too, desires to play a leading role on the world stage, balancing other centers of power such as the European Union and NATO with its political, economic, and military might. Russia has readjusted its foreign policy orientation from one that was Western-looking to one that is increasingly independent in recent years -- even anti-West, deepened by the war in Georgia this summer over the breakaway regions of South Ossetia and Abkhazia. As many have asserted, today's Russia is confident, prideful, wealthy, and interested in reasserting Russia as a great power.

Indeed, some would argue that Russia's chief global foreign policy objective is nothing less than recreating its superpower status. While Russia isn't necessarily looking to become the Soviet Union again, it would like to exert decisive leverage on the international system, as the Kremlin did during the Cold War. To achieve these ends, Russia today maintains its position as the world's second mightiest nuclear weapons state, with over 600 strategic offensive weapons, buttressed by a significant military modernization program to revitalize the once-proud Russian military.

Its ballistic missile force is part of that effort. Russia has one of the world's most active ballistic missile testing programs, planning to test-launch nine ballistic missiles in 2008, according to a senior military commander in May. Russia is putting an average of three mobile and three to four of their newest silo-based Topol-m (ss-27) ICMBs into operation every year. Moscow may double its test launches of intercontinental ballistic missiles after 2009, based on Russian military claims. According to some sources, Russia is already working on a follow-up to the ss-27, based on reports of testing in May. The new version is expected to be equipped with multiple, independently targetable reentry vehicles (MIRVS). Moscow is also testing a new submarine-launched ICBM.

Adding to security concerns, Russia is threatening to pull out of the Intermediate-Range Nuclear Forces (INF) treaty, which eliminated that class of ballistic missiles in a 1987 arms control treaty with the United States. Moscow is uncomfortable with the increase in the number of states around its periphery that now have intermediate range ballistic missiles that did not have them when the treaty was signed over 20 years ago, such as India, Pakistan, Iran, China, and North Korea. This could lead to a bump-up in Russia's missile arsenal.

Treaty Trouble

Shortcomings in the 1970 NPT and the Missile Technology Control Regime (MTCR), moreover, provide further reason to look to missile defenses to help insulate the United States from ballistic missiles and nuclear weapons proliferation. The NPT, which is well-intentioned and may have dissuaded some states from pursuing nuclear weapons, is in dire need of an overhaul. It is rife with loopholes, such as allowing a wide range of nuclear activities closely related to nuclear weapons work. The accord also lacks the requisite teeth to ensure enforcement. North Korea threatened to leave it and then did so with its requisite 90-day notice before its 2006 nuclear test; Tehran ignored its tenets for 20 years before its nuclear activities were disclosed, not by the NPT's Praetorian Guard, the IAEA, but by an Iranian dissident group.

The proliferation of ballistic missiles is not prohibited by any international treaty. The MTCR is a volunteer organization, which has been weakened over time by states that have flouted its principles when advantageous for hard currency, military assistance, or strategic influence. As a result, in recent years, the United States decided that leaving itself deliberately vulnerable to any weapon system or state -- as it did during the Cold War -- was foolish. Deliberate vulnerability can lead to perceptions of weakness, inviting provocation or aggression. In addition, it can lead a potential adversary to use threats, intimidation, blackmail, or coercion to achieve its objectives. In a day of seemingly unstoppable proliferation, the chance that horrific weapons will be used against peaceful nations is a troubling possibility.

Every state has an undeniable right to self-defense. It only makes sense that all reasonable, necessary steps are taken to protect and advance one's national security, especially if the technological capability is emerging to do so, as evidenced by tens of successful missile defense tests. Hitting a bullet with a bullet in the atmosphere, or even space, is now possible. Developing and deploying missile defenses is not about the missile or WMD threat from a single country or even several countries. Missile defense is about protection from these weapons no matter where the threat comes from now -- or in the future.

And despite the range of concerns about missile defense, it should be emphasized that it is a defensive -- not offensive -- weapon. Indeed, the missile defense interceptor warhead does not even contain an explosive charge; traveling at 15,000 miles per hour, it destroys the missile warhead by the sheer force of the collision. Missile defense is like an umbrella; it is needed only if it rains. It threatens no one. It only undermines the capability of one country to threaten or attack another country with its ballistic missiles or WMD. The idea that the deployment of missile defense will provoke an attack is a canard meant to encourage passivity.

The United States has made it clear to concerned states that missile defense does not threaten their security, emphasizing that it is part of an expanding effort to counter the growing ballistic missile threat -- wherever it comes from. Of course, no country should expect to have a veto over America's security. Indeed, those states that oppose missile defense would do better to turn their protests toward Tehran and Pyongyang and other capitals that are driving the need for it with their growing offensive ballistic missile capability, their own missile production, or their proliferation practices. Moreover, some security analysts speculate cautiously that the successful deployment of an effective missile defense may one day convince countries that their pursuit of missiles and WMD should be abandoned as futile endeavors, supporting widely accepted nonproliferation goals.

Cold War-like mutually assured destruction or massive retaliation should not be the only options for policymakers. In the end, it is clear: Missile defense will improve America's security against the growing challenge of ballistic missiles and their unconventional payloads.

Peter Brookes is a Heritage Foundation senior fellow and a former deputy assistant secretary of defense.