The top U.S. and Iranian diplomats say that progress is being made at talks on Iran's nuclear program but that much work remains as a deadline for an agreement approaches.
The United States and five other powers are seeking a deal with Iran that would curb its nuclear activity, which Western states fear is aimed at acquiring nuclear weapons capability, in exchange for sanctions relief.
Officials have been negotiating all week in the Swiss city of Lausanne ahead of a self-imposed end-of-March deadline for a framework agreement, which would be followed by a full deal by June 30.
U.S. Secretary of State John Kerry said on March 19 that talks were facing "tough issues" but that "progress" was being made.
Iranian Foreign Minister Mohammad Javad Zarif told state news agency IRNA, "We are advancing very well but there's still a lot of work to be done."
AFP news agency cited a European diplomat involved in the talks as saying negotiators were "pretty far" from an agreement and accusing Iran of failure to compromise.
Iran says its nuclear program is purely peaceful.