The International Atomic Energy Agency (IAEA) has just rebuked Iran for failing to cooperate fully with international inspectors who are examining whether Tehran is meeting its nonproliferation commitments.

How concerned should we be about this development? What does it mean? By its own admission, Iran has been taking steps to develop the capability to enrich uranium, one of the two methods used to produce weapons-grade fissile material. While Iran says its activities are solely for peaceful production of nuclear power and are permitted by the Non-Proliferation Treaty, once enrichment capability exists, a major barrier to producing a nuclear weapon virtually vanishes. The IAEA condemnation is an indication that the world may be on the verge of a major breakdown of the nonproliferation regime, to say nothing of a huge new source of instability in a critically important region.

The absence of an effective international response to North Korean efforts to develop a nuclear weapons capability may already have resulted in the entry of another country into the ranks of nuclear-capable powers. North Korea not only can be presumed to have reprocessed enough plutonium this year for an additional six to eight nuclear weapons, it reportedly also is working on a uranium enrichment capability to accompany its existing ability to reprocess plutonium from spent fuel rods.

Should Iran now be permitted to develop the capability to enrich uranium, it is almost impossible to imagine that other countries could be dissuaded from creating their own enrichment capabilities and consequently the capacity to produce weapons-grade material for nuclear weapons.

We are at a critical moment. Are we serious in our efforts to prevent nuclear proliferation, or will we watch the world descend into a maelstrom where weapons-grade nuclear material is plentiful and unimaginable destructive capability is available to any country or group with a grudge against society?

Staring into that abyss should stir us to action. What can we do? The United States, Britain, France and Germany have already shown an encouraging, if insufficient, degree of cooperation with respect to the Iranian nuclear program. Russia has been the principal source of assistance in the development of Iranian nuclear power. But Russia has already informed Iran that it would expect spent nuclear fuel from the Bushehr plant to be returned to Russia, appearing to indicate that it too has no interest in allowing Iran to develop a nuclear weapons capability.

This situation should allow these five powers to deepen their cooperation to the point of presenting a united front to Iran. They could announce that they would be prepared to give Iran full assistance in developing nuclear power generation capability, under appropriate safeguards. They could offer to guarantee an adequate supply of nuclear fuel for Iranian power reactors at favorable rates and to remove spent nuclear fuel from Iran. In return, Iran would be required to forswear any attempt either to enrich uranium or to reprocess spent nuclear fuel.

It must be acknowledged that this would be a difficult offer for the United States to make, requiring it to put aside its serious concerns about a range of other objectionable Iranian behavior. But the nonproliferation stakes are so great that they warrant addressing this issue separately.

If Iran is sincere in its protestations that it seeks nuclear energy only for power generation, this would be by far the most efficient and economical way for it to reach that goal. Agreement could also pave the way for discussions on broader issues of concern among the parties, including security questions.

Should Iran reject such an offer, it would be clear that its objective is the acquisition of nuclear weapons. In that event, the issue should be taken to the U.N. Security Council, and the most serious forms of sanction and isolation should be applied.

But while Iran is an urgent matter, we will not succeed in dealing with it if we treat it as an isolated case. Like Iran, Brazil has announced its intention to construct a uranium enrichment facility. If we give Brasilia a pass at the same time that we are bearing down on Tehran, it not only will send exactly the wrong message to would-be proliferators but will sharply diminish any prospects for success with Iran.

Acquiescing in the Brazilian enrichment program would have the effect of dividing nuclear power aspirants into good guys and bad. Such an approach would provide a powerful weapon to Iran as it seeks to rally international support for its "peaceful" nuclear program and split us from the Europeans and the Russians.

Our goal instead should be to delegitimize the spread of uranium enrichment and plutonium reprocessing facilities to any country, because these capabilities are the linchpin of any program to develop nuclear weapons.

Put simply, the way Brazil is dealt with could prove to be one of the keys to dealing with the Iranian nuclear problem, either by persuading Tehran to abandon its nuclear weapon ambitions or by rallying the international community to crack down on Iran if it does not. We therefore should make the same offer to Brazil as to Iran and make clear the consequences if Brazil turns down that offer.

These steps are certainly no substitute for a carefully thought-out general program to enhance the safeguards of the Non-Proliferation Treaty and otherwise improve the effectiveness of the nonproliferation regime. But if we do not act swiftly and decisively now, attempts to provide a future comprehensive framework will be worse than fruitless.

Now is the moment of truth.

The writer was national security adviser to presidents Gerald Ford and George H.W. Bush. He is president of the Forum for International Policy.