Diplomats seeking to limit Iran's nuclear program have long said they wouldn't keep bargaining if officials in Tehran proved unwilling to budge. But after a year of frazzling negotiations and two missed deadlines, the diplomats have done just that.
Six world powers and Iran failed to meet the latest cutoff date, Nov. 24, for a comprehensive deal and instead extended negotiations for seven months. Diplomats who had gathered in Vienna said that new ideas were raised in the final hours of talks that merited study and that they justified setting yet another deadline.
"We would be fools to walk away," Secretary of State John F. Kerry told reporters.
Although deep divisions remain on core issues, diplomats fear a complete breakdown in talks would raise risks for all sides: advances in Iran's nuclear program, a greater danger of war, or new U.S. and European sanctions that could further batter the Iranian economy.
World powers have been trying since 2003 to negotiate curbs on Iran's uranium enrichment program. Iran insists the program is for energy and other civilian purposes, but Western governments believe that Tehran is seeking bomb-making capability and thus poses a threat to world security.
The deal being sought would involve a basic trade-off: The world powers would ease U.S., European and United Nations economic sanctions on Iran if it agreed to restrictions aimed at preventing it from building a nuclear bomb.
Iran and the six powers — the United States, Britain, France, Germany, Russia and China — have been negotiating under the terms of an interim agreement worked out in November 2013. The so-called joint plan of action gave Iran limited relief from sanctions in exchange for a halt to some of its most worrisome nuclear activities.
Over the course of the year, negotiators made headway in several areas.
Iran agreed to stop adding centrifuges, the machines that can enrich uranium to convert it to bomb fuel. It also agreed to stop enriching uranium to a 20% purity, which is close to the grade at which it can be used for bomb fuel.
Iranian officials also promised to redesign a partially built heavy-water research reactor at Arak to reduce its output of plutonium, another potential bomb fuel. They agreed to more intrusive monitoring of nuclear facilities by U.N. inspectors and said they would convert a bomb-resistant underground enrichment facility at Fordow into a research site.
Yet the remaining differences have defied solution.
Iran, which considers its program a symbol of national achievement, is willing to freeze some activities but has rejected demands to dismantle its $100-billion nuclear infrastructure. And by 2021, it wants to expand its enrichment capability twentyfold by adding thousands of centrifuges.
Tehran also wants immediate relief from travel restrictions and tough sanctions on such items as oil sales. The six world powers insist that the penalties can be removed only gradually, as Iran proves it will make good on its promises.
Iranian Foreign Minister Mohammad Javad Zarif developed a good rapport with the Western negotiators and convinced them of his commitment to getting a deal. But Iran's supreme leader, Ayatollah Ali Khamenei, has proved a different story.
Khamenei, who built his career on strident opposition to the West, has set forth tough demands and stuck to them, Western diplomats say.
The negotiators had hoped that Iran would make concessions in the final negotiating sessions in Oman and Vienna last month. But that didn't happen.
When the latest talks ended, division remained on several key issues: how much enrichment capacity Iran would be allowed to keep, how long the agreement should last, how closely Iran's program would be monitored, how much nuclear research it could conduct, and how it would redesign the Arak reactor.
Some Western officials concluded that Khamenei was more worried that better relations with the West would undermine strict Islamic rule than that new sanctions and further squeezing of the economy would hurt Iranians.
Many Western officials fear prospects for a deal declined with the failure to reach agreement last month. Republicans will take control of the Senate in January and are threatening to impose new sanctions. Hard-liners in Tehran also may be emboldened by Zarif's failure to deliver sanctions relief.
Yet both sides have reasons to want the bargaining to continue under the terms of the interim agreement.
From Iran's point of view, it provides at least some easing of sanctions, and it averts the threat of additional penalties or an armed attack by the United States or Israel on its nuclear sites.
From the Western perspective, continued negotiations allow the possibility of a deal and provide some limits on Iran's nuclear activities.
And the alternatives are not great. Bombing Iran's nuclear sites could embroil the United States in another bitter conflict in the Middle East while only halting Iranian progress for a couple of years.
A further ratcheting-up of sanctions might force Iranian officials to give more ground in negotiations. But it might also drive them away from the bargaining table.
And it could unravel the current system of sanctions by convincing key non-Western oil purchasers — China, India, Turkey — that the West deserved the blame for the failure of diplomacy. If that's their conclusion, they may decide to flout the sanctions and increase purchases of Iranian oil.
Edward Levine, a former longtime Senate foreign affairs advisor, said there is a danger that the seven governments will decide they'd prefer to live under the current limited rules and keep talks going rather than take the bigger risks required for a comprehensive deal.
"There's a risk that it will impede progress to a real deal because it's an easy second-best solution," Levine said last month at a Brookings Institution forum.