Major powers and Iran were pushing each other for concessions on Friday ahead of an end-March deadline for a preliminary nuclear deal, with Tehran demanding an immediate end to sanctions and freedom to continue sensitive atomic research, officials said.
Tehran and six major powers - the United States, Britain, France, Germany, Russia and China - are meeting in Lausanne, Switzerland, to hammer out a political framework accord by the end of this month that would lay the foundations for a full deal by June 30.
Under a final settlement, Tehran would halt sensitive nuclear work for at least a decade and in exchange, international financial and oil sanctions on Iran would be lifted. This would aim to end the country's 12-year nuclear standoff with the West and reduce the risk of war in the Middle East.
While all sides agree they have been inching closer to a deal, there are major disagreements that have prevented a resolution.
Tehran insists on the freedom to continue research on advanced centrifuges, machines that purify uranium for use in nuclear power plants or, if very highly enriched, in weapons, at an underground facility, and the immediate lifting of all UN sanctions and the most severe US and European Union sanctions.