Kerry axes US return for Iran talks
US secretary of state John Kerry has cancelled plans to return to the United States in order to remain at Iran nuclear talks in Switzerland amid signs of trouble in the negotiations.
The State Department said Mr Kerry had been looking forward to an event honoring his late colleague Edward Kennedy, the dedication of the Kennedy Institute in Boston, alongside the family of the late Massachusetts senator.
But "given the ongoing nuclear negotiations in Switzerland, the secretary regrets he will not be able to share this special time with them in person", it said.
Mr Kerry served in the Senate with Mr Kennedy for nearly 25 years and the two were close friends.
His decision to stay comes as the talks appear to have hit obstacles ahead of a March 31 target for the outline of a final deal to be negotiated by the end of June.
Officials have spoken of the hurdles in general terms, citing Iranian resistance to limits on research and development and demands for more speedy and broad relief from international sanctions.
With just three days to go, negotiators were meeting multiple times in various formats. Mr Kerry has been in discussions with Iranian foreign minister Mohammad Javad Zarif in the Swiss town of Lausanne since Thursday.
The foreign ministers of France and Germany arrived yesterday and those from Britain, China and Russia are due to arrive today.
The State Department said late yesterday that "serious but difficult work" remained for negotiators and the pace of discussions is expected to intensify as "we assess if an understanding is possible".
Iran says its nuclear ambitions are purely peaceful but other nations fear it is seeking to develop weapons.
Progress has been made on the main issue: The future of Iran's uranium enrichment programme. It can produce material for energy, science and medicine but also for the fissile core of a nuclear weapon.
The sides have tentatively agreed that Iran would run no more than 6,000 centrifuges at its main enrichment site for at least 10 years, with slowly easing restrictions over the next five years on that programme and others Tehran could use to make a bomb.
The fate of a fortified underground bunker previously used for uranium enrichment also appears closer to resolution.
Officials said the US may allow Iran to run hundreds of centrifuges at the Fordo bunker in exchange for limits on centrifuge work and research and development at other sites.
The Iranians would not be allowed to do work that could lead to an atomic bomb and the site would be subject to international inspections.
Instead of uranium, any centrifuges permitted at Fordo would be fed elements used in medicine, industry or science, the officials said.
Even if the centrifuges were converted to enrich uranium, there would not be enough of them to produce the amount needed to make a weapon within a year - the minimum time frame that Washington and its negotiating partners demand.
A nearly finished nuclear reactor would be re-engineered to produce much less plutonium than originally envisaged.
Still problematic is Iran's research and development programme. Tehran would like fewer constraints on developing advanced centrifuges than the US is willing to grant.
Also in dispute is the fate of economic penalties against Iran. In addition, questions persist about how Iran's compliance with an agreement would be monitored.