"What will stop Iran from getting the bomb?" Iran Watch posed this timely question recently to a group of experts convened for a roundtable discussion.(*) Their answer was distressing. They concluded that if the world continues down its present path, Iran is likely to succeed in its nuclear weapon quest.

The experts ruled out any immediate action by the United Nations to punish Iran as impracticable. Why? Because economic sanctions or the use of force would require unity among U.N. Security Council members, which currently does not exist. The only hope of convincing Iran to abandon its nuclear ambitions, they found, is through vigorous international diplomacy. However, none were optimistic about the chances of diplomatic success.

For diplomacy to have a chance of working, three things would have to happen. First, the United States must add its weight to the negotiations between Iran and Europe, which means not only threatening punitive measures if Iran fails to cooperate but offering Iran inducements if it does. Second, Russia and China must support the European effort and pressure Iran to accept the bargain being proffered. Third, Iran's neighbors must warn Tehran that they might follow its nuclear example, which could escalate the conventional arms race in the region to the nuclear level.

This iterative diplomatic process might help build an international consensus-especially among permanent members of the U.N. Security Council-about the dangers of a nuclear-armed Iran. And if negotiation eventually fails, the diplomatic ground work could help consolidate support for more intrusive inspections, sanctions or the use of force.

Unfortunately, the prospect that any of these steps will be taken-let alone all of them-is slim. If recent remarks by Secretary of State Condoleezza Rice and Vice President Dick Cheney are to be believed, the Bush administration is not ready to negotiate. As for Russia and China, they show no signs of allowing proliferation concerns to get in the way of their lucrative economic ties with Iran. And Iran's neighbors have been noticeably quiet on the issue, perhaps unwilling to take a tough line and appear to be marching in lock step with the United States.

Even if all these countries were to band together, it is not clear that Iran would be swayed. Iran has so far refused to give up the most dangerous parts of its nuclear program-those that will allow production of enriched uranium and plutonium, the materials that fuel nuclear weapons. Once Iran can produce these materials domestically, the path will be open to its first nuclear weapon. Iran's President Mohammad Khatami said recently that "we consider enrichment our clear right and will never give it up." And a number of other Iranian officials have insisted that the present deal with Europe that suspends uranium enrichment is only temporary.

Iran does not need to make plutonium or enriched uranium to run its civilian nuclear energy program. But producing them would make it impossible for the International Atomic Energy Agency to verify that Iran is not conducting secret nuclear work. And while a more robust inspection regime like the Agency's Additional Protocol raises the risk to Iran of conducting secret work, it by no means guarantees the absence of such activity. Only more intrusive inspections, in which inspectors are allowed "anyplace, anytime" access-including to sensitive military sites-would provide a strong guarantee against cheating. But Iran would probably reject such inspections as a grave infringement on its national sovereignty.

The European negotiations with Iran do provide an opportunity. By making them more vigorous, there is at least a chance that Iran could be persuaded to change its mind and step off the road to the bomb. Without the participation of the United States, Russia and China, however, the talks will probably fall apart.

If they do, the world should be ready to face a nuclear-armed Iran. There is little chance that the U.N. Security Council will agree to strong economic sanctions unless Iran does something dramatic to trigger worldwide outrage, which is not likely. There is even less of a chance that the Security Council will approve military action against Iran. And the unilateral use of force by the United States against Iran might trigger "asymmetric" retaliation-in the United States, Europe or Israel-that could leave the overextended U.S. armed forces without a practical response.

For diplomacy to work, a number of diverse states must change their priorities. They must capitalize on the narrow opening created through Europe's initiative and cooperate to draw Iran back from the nuclear brink. Today, the signs from Washington, Moscow, Beijing and the Middle East are not promising. In the end, the world may prove unwilling to prevent Iran from developing a nuclear weapon.

* This article is based in part on the conclusions of a panel of five experts on weapons proliferation, Iran and the Middle East who met in November under the auspices of the Wisconsin Project on Nuclear Arms Control.