Foreign ministers are converging on Lausanne this weekend in a bid to finalise a deal with Iran over the future of its nuclear programme, amid reports that negotiators are close to a general understanding.



The draft understanding, according to diplomats at the talks, is two or three pages long and lays down the outline of a much more detailed and technical agreement that is due to be completed by the end of June. It is thought to include a ceiling for Iran’s uranium enrichment capacity, tentatively agreed at 6,000 centrifuges, and a limit for its stockpile of low enriched uranium. It would also specify a timetable for the lifting of sanctions and the duration of the restrictions on the Iranian programme, thought to be between 10 and 15 years.

“We’re moving forward,” Iranian foreign minister Mohammad Javad Zarif said on Saturday night as he continued talks with US secretary of state John Kerry.

“I think we can in fact make the necessary progress to be able to resolve all the issues and start writing them down in a text,” Zarif said.

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However, diplomats warned that not all the key points were agreed, and there were differences over whether they would be made public and in what form.

“The talks have been long and difficult. We’ve advanced on certain issues, not yet enough on others,” the French foreign minister, Laurent Fabius, told reporters outside the talks venue, a lakeside hotel, on Saturday. He said he had come to ensure that any accord would be robust, ensuring the transparency and close monitoring of Iran’s nuclear activity.

His German counterpart, Frank-Walter Steinmeier, arrived in Lausanne soon afterwards to join Kerry and Zarif, who have been in discussions since Thursday. After having lunch with the Europeans, Kerry went on a bicycle ride along the shores of Lake Geneva, leaving Steinmeier and Fabius to hold bilateral meetings with Zarif.

The European Union foreign policy chief, Frederica Mogherini, was expected to fly in on Saturday night, while Britain’s foreign secretary, Philip Hammond, and his opposite numbers from Russia and China, Sergei Lavrov and Wang Yi, were due to join the negotiations on Sunday.

All the delegations have said they are focused on overcoming the last few hurdles to an historic deal by the end of Sunday, although the self-imposed deadline is the end of March. However, western diplomats are wary that if negotiations drag on to Tuesday night and into the early hours of Wednesday morning, any agreement will risk being labelled as the April Fool’s Deal by hardline sceptics.

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Kerry is due to fly back to Washington early in the week, in a bid to persuade Congress not to impose new sanctions later in April that could kill off a deal before it can be finalised in June.

“Here, with a view of the Swiss mountains, I’m reminded that as one sees the cross on the summit, the final metres are the most difficult but also the decisive ones,” Steinmeier said on arrival.

If a framework deal is achieved, it is likely to be announced in Geneva rather than Lausanne. The Iranians are said to prefer any ceremony to be carried out under the auspices of the United Nations institutions in Geneva, rather than at a luxury hotel whose last appearance on the history pages was as the venue of the Lausanne Treaty of 1923, which finalised the dismantling of the Ottoman Empire and set the borders for modern Turkey.