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.