U.S. Secretary of State John Kerry and his Iranian counterpart Mohammad Javad Zarif resumed nuclear talks on Monday in the Swiss city of Lausanne to try to narrow gaps before a March 31 deadline for a political agreement.
The meeting included U.S. Secretary of Energy Ernest Moniz and Iran's nuclear chief Ali Akbar Salehi, who also met on Sunday to negotiate technical details on how to curb Iran's nuclear programme.
Kerry has urged Iran to make concessions that would allow six world powers to reach a political framework agreement for a nuclear deal with Tehran that would lift sanctions in exchange for curbs on Tehran's nuclear programme.
The parties have set a June 30 deadline to finalise an accord. Iran and major powers will meet this week in Lausanne but the date has not been announced yet.