There is no point setting a deadline for Iran to fulfill its nuclear non-proliferation obligations unless it is enforced.

Unfortunately, the United Nations Security Council appears reluctant to enforce its own demand. That probably explains why Iran seems so unconcerned about the now-passed Aug. 31 deadline to freeze its uranium-enrichment program.

Even as the "deadline" approached, Iran continued to shrug off its obligations under the Nuclear Non-Proliferation Treaty. President Mahmoud Ahmadinejad apparently calculated that, as long as Iran keeps telling the world it is willing to engage in endless talks (without shutting down its suspect activities), the Security Council will fail to follow through on its threat to impose sanctions.

He undoubtedly is betting that Iran's friends, Russia and China, will use their veto power to water down any sanctions. Sadly, he's probably correct on both counts.

That explains why, now that the deadline has passed, the United States should take immediate action to mobilize support for the strongest possible sanctions at the Security Council and press its allies to follow through with even stronger sanctions outside the U.N. framework, where Russia and China will not be able to protect Iran from the consequences of its nuclear defiance.

Iran is thumbing its nose at the Security Council. Shortly before the deadline, President Ahmadinejad ostentatiously opened a heavy-water reactor that is capable of producing plutonium, the preferred fissile material for arming nuclear warheads for ballistic missiles. That gives Iran yet another possible route to attain nuclear weapons.

Meanwhile, the EU-3's (Britain, France, and Germany) on-again, off-again negotiations with Tehran from 2003 to 2005 accomplished little except to allow Iran to defuse and delay international action and buy more time for its nuclear-weapons program. Iran continues to stall.

In its non-response to the Security Council's demand to halt its uranium enrichment, Tehran included a 21-page document that sought to clarify "ambiguities" in the incentives offered by the EU-3 and the United States if it suspends its suspect activities. This is another Iranian attempt to bog down the issue in endless talks.

An international response to Tehran's stubborn refusal to abide by its treaty commitments is long overdue. Iran has never paid any price for its failure to disclose its nuclear activities, which were discovered in 2002. It is high time that Iran be penalized for its continued refusal to fully cooperate with the International Atomic Energy Agency's investigation of its clandestine nuclear program.

In addition to pressing for U.N. sanctions (aimed at the Iranian regime, not the people), the U.S. should aim for punishment outside the U.N. framework. Washington should press its European and Asian allies, along with other countries threatened by an Iranian nuclear-weapons program, to impose sanctions including a ban on transfers to Iran of arms, dual-use technology, foreign investment and loans.

The Iran Freedom and Support Act, now before Congress, would improve the administration's leverage with Iran. It would strengthen and permanently reauthorize the Iran-Libya Sanctions Act (ILSA), which imposes economic sanctions on companies that invest more than $20 million per year in Iran's oil industry. ILSA is set to expire soon if not renewed. Once the act is reauthorized, the Bush Administration should use it to penalize companies that invest in Iran's oil industry and thereby help Iran to finance its nuclear activities, military buildup and support for terrorism. The Iran Freedom and Support Act also would authorize the president to provide assistance to Iranian opposition groups that support democracy, oppose terrorism, and advocate nuclear nonproliferation in Iran.

Meanwhile, we need to learn more about Iran's clandestine nuclear-weapons program, as well as its chemical weapons, biological weapons and ballistic-missile programs. The House Permanent Select Committee on Intelligence recently released a report that concluded, "U.S. policymakers and intelligence officials believe, without exception, that the United States must collect more and better intelligence on a wide range of Iranian issues." Such improved intelligence would be especially valuable if it ultimately proves necessary to use military power as a last resort to defuse Iran's potential nuclear threat.

Tehran's strategy is clear: Just as it has since 2002, it will pursue diplomatic gambits to drive a wedge into the tentative coalition of states opposing its nuclear-weapons program and stall action while it builds its nuclear capabilities.

So far, it has evaded any consequences for its nuclear duplicity. The U.S. must take the lead to raise the diplomatic, economic, political and possible military costs to the Ahmadinejad regime of its prohibited nuclear activities. That is the only way to ensure that, in the future, Iran actually heeds the deadlines set by the international community and abides by its international legal commitments.

James Phillips is Research Fellow for Middle Eastern Affairs in the Douglas and Sarah Allison Center for Foreign Policy Studies, a division of the Kathryn and Shelby Cullom Davis Institute for International Studies, at the Heritage Foundation.