The list of international nuclear problems continues to grow. The U.S. war victory over Iraq has presumably ended concerns about that country's efforts to develop nuclear weapons. North Korea's nuclear program is the current focus of international attention. Now the U.S. is ringing the alarm over Iran's efforts to develop nuclear weapons. Washington is taking its concerns to the International Atomic Energy Agency in hopes of winning a declaration that Tehran is in violation of the Nuclear Nonproliferation Treaty, or NPT. If the allegations are true -- and the suspicions appear justified -- then action is warranted. But it would be much better if the international community acted rather than the U.S. taking it upon itself to police the NPT.

Iran has long had a nuclear-energy development program, but recent disclosures have raised important questions about its purposes. Most of the international focus has been on a nuclear reactor in Busherh, which has been built with Russian assistance and has the potential to produce weapons-grade plutonium. More recently, attention has shifted to Natanz, in central Iran, a site not known to nuclear experts until last year. The government in Tehran has revealed that it built a uranium-enrichment plant there. More worrisome are large underground structures that intelligence experts suspect contain centrifuges used to produce highly enriched uranium, a fuel that could be used for nuclear weapons.

The Iranian government maintains that the Natanz site is for peaceful purposes. It has let IAEA inspectors visit several of its nuclear facilities and has no objection to continuing discussions on signing the IAEA's Additional Protocol, which would allow tighter inspections of nuclear facilities. Iran's claims appear to have gained the support of the IAEA after Mr. Mohamed ElBaradei, IAEA director general, led a team of inspectors to Natanz in February.

The U.S. is not convinced. Assistant Secretary of State for Nonproliferation John Wolf has called Iran's nuclear program "the most fundamental challenge ever faced by the Nonproliferation Treaty." American experts have concluded that the Natanz site is a weapons facility. They also question the very rationale for developing nuclear energy when Iran is rich in so many other fuel sources. A State Department spokesman has pointed out that the energy-production potential of the natural gas that Iran flares off annually exceeds that of the desired reactors.

Russia will play a key role in settling this issue. Washington believes that Russian scientists are clandestinely supplying Tehran with nuclear technology. Moscow denies the accusation, countering that "no grounds exist" for saying that Iran is in breach of its IAEA obligations. Russia has said Iran is incapable of building nuclear weapons, but earlier this year Russian officials conceded that they could not determine whether Iran was secretly developing nuclear arms.

The United States wants the issue on the IAEA agenda for a meeting scheduled next month. Washington is pushing Russia and Western European nations to back the hardline position that Iran has violated the NPT. Such a declaration could lead to harsh action, including economic sanctions, by the United Nations. While the U.S. is ready to let the IAEA take the lead on this issue, President George W. Bush said the U.S. is ready to step in if the world body does not.

Those are troubling sentiments. Suspicions surrounding Iranian action and motives involve broader concerns about terrorists getting their hands on weapons of mass destruction as well as lingering distaste in the U.S. for the Iranian regime. Iran was a member of Bush's "axis of evil," along with Iraq and North Korea. The Bush administration has denounced Tehran's support for Hezbollah and other militant groups linked to terrorism in the Middle East. There are rising concerns that the victory over Baghdad may encourage the U.S. to take aggressive -- though not necessarily military -- action against Iran as well.

Iran's relations with the U.S. are important for the entire region. Support for terrorists has the potential to destabilize the Middle East. Unfortunately, the issue is politically and emotionally charged in both capitals, with conservatives in both countries using the prospect of engagement as a club to beat moderates. Reportedly, there have been secret contacts between the two governments. That is a promising start, but no progress can be expected until the discussions move out of the shadows and the public in both countries accept such overtures.

In the current hothouse environment, the prospect of censure by the IAEA and the U.N. will not be helpful. But violation of the NPT and the prospect of yet another nuclear proliferator is unacceptable. Iran must fully disclose its nuclear ambitions -- and put an end to suspicions that it seeks nuclear weapons.