Whether or not Iran ultimately agrees to talk under these conditions, the United States has already strengthened its hand with European allies, Russia and China, all of whose support would be needed for any successful resolution of the Iranian nuclear crisis.

The Russians, Chinese, Europeans and Americans quickly followed up Secretary Rice's announcement with agreement on a new tactical approach. It would, for now, suspend discussions of Security Council sanctions and instead offer a jointly agreed set of incentives aimed at persuading Tehran to suspend nuclear work and come to the bargaining table. If Iran spurns that conciliatory approach, Washington is sure to put sanctions back on the international agenda.

The next few days and weeks will be delicate. Iran makes much of its right, under international law, to enrich uranium for power plants. But it is much less eager to talk about its unambiguous obligation, under the same treaty, not to abuse that right for purposes of building nuclear weapons. Its current enrichment programs threaten to cross that critical line. Tehran would not be giving up any rights by suspending enrichment-related activities. It has already done so twice before. Many other countries with exactly the same legal right to enrichment and reprocessing have wisely chosen not to engage in those problematic activities.

There is only one successful resolution worth talking about — a verifiable commitment by Iran not to develop the capacity to build nuclear weapons. Whether this comes about through incentives, punishments or some combination of the two does not matter very much, so long as it comes about.