Iran and six major powers are unlikely to meet a Nov. 24 deadline to reach a final deal to lift international sanctions on Tehran in exchange for curbs on its nuclear program, officials say.
Western and Iranian officials said the two sides would probably settle for another interim agreement that builds on the limited sanctions relief agreed a year ago as they hammer away at their deep disagreements in the coming months.
"We could see the outline of a final deal emerging by Nov. 24 but probably not the deal itself," a Western official said.
Iran, the United States, Britain, France, Germany, Russia and China, along with the European Union's former foreign policy chief Catherine Ashton are locked in talks which have shuttled between Brussels, Oman and Vienna.
Publicly all sides say it is still possible to reach a comprehensive agreement to end all sanctions in return for long-term limits on Iran's nuclear program to ensure it never makes an atomic weapon.
Privately, expectations of what is achievable when senior foreign ministry officials begin the final week of talks next Tuesday in Vienna are much more modest.
"What is very likely is to reach a more detailed version of the Geneva agreement, enough to tackle the recession in Iran and also to extend the talks," a senior Iranian official said, referring to the interim accord reached in Geneva a year ago which set the current talks in train.
While denying it seeks to make nuclear weapons, Iran has refused to halt its uranium enrichment program, prompting crippling U.S., EU and UN sanctions that have caused Iranian oil revenues to plummet and inflation and unemployment to soar.
Some diplomats said a simple extension of the negotiations was possible, and a senior Iranian official said this could be until March. They were extended already for four months in July.
One senior Western diplomat close to the talks, who like the Iranian official spoke on condition of anonymity, insisted that the six powers were still doing everything possible to get a solid, comprehensive agreement this month as planned.
"I can categorically deny that behind closed doors ambitions are more modest," the official said. "Everyone is pushing very hard for the 24th." Russia's senior negotiator, Deputy Foreign Minister Sergei Ryabkov, said Wednesday he was optimistic a deal could be reached in Vienna.
Western and Iranian officials said a collapse of the talks was unlikely as all sides want an end to the 12-year dispute.
One Western diplomat said it remained unclear whether the Iranian negotiating team, led by Foreign Minister Mohammad Javad Zarif and his deputy Abbas Araqchi, had a mandate to make the kinds of compromises needed for a deal.
"We just don't know if [Supreme Leader, Ayatollah Ali Khamenei] will let them reach the kind of deal we want," the diplomat said.
The sticking points remaining are how many uranium enrichment centrifuges Iran can have and the speed of lifting sanctions, mainly on oil exports and the banking and insurance sectors.
The United States, France, Britain and Germany would like the number of centrifuges to be in the low thousands, while Tehran wants tens of thousands in operation. It now has about 19,000 installed and around 10,000 in operation.
One idea is to transfer some of Iran's enriched uranium to Russia for storage. Iranian officials said they were theoretically open to this and Western officials said it could be a step in the right direction.
A senior U.S. official said most of the technical annexes to an agreement are complete and they are now working on the political document.
Iran has made clear it is prepared to help international efforts to defeat Islamic State militants in Syria and Iraq, and associated that offer with potential concessions in the nuclear talks, but Western officials reject the idea.
Iran is worried that the Obama administration's ability to make a deal has been severely reduced by last week's congressional elections, a European diplomat said. Republicans now control both houses of the U.S. legislature and have taken a harder line than President Barack Obama's Democrats on Iran.