Iranian Foreign Minister Mohammad Javad Zarif and top US diplomat John Kerry will meet in Geneva this weekend for talks on Tehran's nuclear program, Iranian and American officials said Thursday.
Iran and world powers are trying to strike a deal that would prevent Tehran from developing a nuclear bomb in return for an easing of punishing international economic sanctions.
Zarif and Kerry will hold two days of discussions from Sunday after their diplomats begin bilateral talks on Friday, Iran's deputy foreign minister Abbas Araqchi said, quoted by the IRNA news agency.
State Department spokeswoman Jen Psaki confirmed the two men would meet on Sunday in Geneva as "part of the ongoing nuclear negotiations" after top US negotiator Under Secretary Wendy Sherman first meets with the Iranian delegation.
Araqchi added there would then be meeting of the so-called P5+1 -- Britain, China, France, Russia, the United States and Germany -- which is seeking to thrash out a complex deal with Iran.
Psaki said the schedule was still being worked out, but did not rule out other multilateral meetings.
Tehran denies seeking atomic weapons, but Western powers remain unconvinced its activities are solely aimed at peaceful civilian energy production.
Under an interim deal struck in November 2013, Iran's stock of fissile material has been diluted from 20 percent enriched uranium to five percent in exchange for limited sanctions relief.
But skepticism is mounting about whether a permanent agreement is possible after two deadlines for a comprehensive deal were missed.
- 'Complicated' negotiations -
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Separately, the International Atomic Energy Agency said in a report Thursday that Iran still had not responded to specific questions on allegations that it had previously carried out nuclear weapons research.
Tehran has consistently rejected the claims, and failed to provide an explanation due in August 2014 on two specific points.
The world powers are now working toward reaching a political framework for a deal with Iran by March 31, with the final technical details to be laid out in a comprehensive accord by June 30.
"The problem is that for now, Iran has not yet demonstrated to us that it intends to renounce the bomb," French President Francois Hollande said Thursday.
"But once that is done, the agreement will be concluded."
Amid growing rumors that a deal may be within reach, Psaki refused to be drawn on whether the two sides were close, saying there was still six weeks to go.
She also dismissed Israeli claims that their officials knew what was being proposed and said it was a "bad deal."
"There isn't a deal, so it's hard for anyone to know," Psaki hit back.
Israeli Prime Minister Benjamin Netanyahu is due to make a controversial address to the US Congress on March 3, to outline his fears about the US outreach to its foe Iran.
But nearly two dozen US House Democrats on Thursday urged the postponement of the speech saying it could torpedo the delicate negotiations.
"Our relationship with Israel is too important to use as a pawn in political gamesmanship," the lawmakers said.
"We strongly urge you to postpone this invitation until Israelis have cast their ballots and the deadline for diplomatic negotiations with Iran has passed."