Despite endless talks, the United States, Czech Republic and Poland still have not reached an agreement on fielding a missile defence system that would protect the US and Europe from the growing threat of long-range ballistic missiles.

With Iran continuing to enrich uranium, the possibility of 'loose nukes' in Pakistan and an active year for ballistic missile tests in 2007 led by China, Iran and Russia, tarrying over this decision is a mistake: one that will only serve to undermine transatlantic security in the face of current and potential future threats.

In recent years, the US decided that leaving itself deliberately vulnerable to any weapon system or state - as it did during the Cold War - was foolish, and rightfully so. Deliberate vulnerability can lead to perceptions of weakness, inviting provocation or aggression from another nation or transnational actor, such as a rogue state or terrorist group.

In addition, being weak and vulnerable can lead a potential adversary to use threats, intimidation, blackmail or coercion to achieve its objectives. In a day when North Korea is a nuclear power and Iran is still very likely on the path to becoming one in the not too distant future, the chance that these weapons will be used against peaceful nations is a troubling possibility - one that we must guard against.

Every state has an undeniable right to self-defense - and it only makes sense that we take all necessary steps to protect ourselves. It is even more logical if we have the emerging capability to do so, as witnessed by over 30 successful missile defense tests by the US alone. As a matter of fact, hitting a bullet with a bullet in space is possible.

Even though states such as North Korea and Iran are good examples of the need for missile defense today, developing and deploying missile defenses is not about a missile or a weapon of mass destruction (WMD) threat from a single country, or even several countries. Missile defense is about protection from these weapons, no matter where the missile threat comes from, now or in the future.

There are other advantages in fielding a missile defense system in Europe. Hosting a transatlantic missile defense system will deepen and further unify the security relationship between European NATO members, especially Poland and the Czech Republic, and the U.S., enhancing mutual national security against external threats from ballistic missiles or the WMDs they might carry.

Despite Russian complaints about missile defense, it should be emphasized that missile defense is a defensive - not offensive - weapon. Indeed, the missile defense warhead does not even contain an explosive charge; travelling at 15,000 miles per hour, it destroys the missile warhead by the sheer force of the collision.

This means that missile defense threatens no one, including Russia, which should not expect to have a veto over the security of Europe or the U.S. In truth, missile defense only undermines the capability of one country to threaten or attack another country with its ballistic missiles and WMDs. War games have shown that missile defense stabilizes rather than destabilizes the security environment because it is a defensive, not an offensive, weapon.

The idea that the deployment of missile defense in Europe will provoke an attack against Poland, the Czech Republic or any country that hosts missile defenses, such as the UK or Denmark, which have missile defense radars, is a canard meant to encourage passivity. Defensive systems do not provoke attack. It is vulnerability or weakness that invites attack - not a posture of resolve and strength.

The U.S. and other have made it clear to Russia that missile defense does not threaten Russian security.

Talks have emphasized that missile defense is part of an expanding effort in Europe to counter the growing ballistic missile threat, wherever it comes from.

Indeed, Moscow would do better to turn its protests toward Tehran and Pyongyang: capitals that are driving the need for missile defense because of their growing offensive ballistic missile capability.

Moreover, some security analysts speculate - though cautiously - that the successful deployment of an effective missile defense system may one day convince countries such Iran and North Korea that their pursuit of missiles and WMDs should be abandoned as futile endeavors, thus supporting widely accepted non-proliferation goals.

Considering the fact that just 10 years ago there were only six nuclear weapons states and today there are nine - and 25 years ago, nine countries had ballistic missiles while today there are 27 - the trend is not positive. It only makes sense that we take steps such as missile defense to ensure our national security with options beyond the threat of mutually assured destruction or massive retaliation.

In the end, it is clear: missile defenses will improve U.S. and European security against the growing challenge of ballistic missiles and their unconventional payloads. It is high time the U.S., Poles and Czechs strike a deal, enhancing both transatlantic ties and our common security.

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