U.S. Secretary of State John Kerry met on Sunday with Iranian Foreign Minister Mohammad Javad Zarif, The Associated Press (AP) reported.
The talks were expected to focus on the prospects of reaching an agreement on reducing Tehran's atomic activities in exchange for an end to nuclear-related sanctions on Tehran.
The meeting Sunday comes on the third day of the latest round of nuclear talks between Iran and six world powers - the United States, Russia, China, Britain, France and Germany.
Iran and the powers failed to meet a July 20 target date for an agreement and have extended the deadline to November 24.
On Saturday it was reported that Iran and the U.S. are now discussing a new proposal that would leave much of Tehran's enriching machines in place but disconnected from feeds of uranium
The talks have been stalled for months over Iran's opposition to sharply reducing the size and output of centrifuges that can enrich uranium both to levels needed for reactor fuel or the core of nuclear warheads.
Iran says its enrichment program is only for peaceful purposes, but Washington fears it could be used to make a bomb.
The Islamic Republic has been taking an increasingly aggressive line in demanding its "right" to enrich uranium, with Iranian Supreme Leader Ayatollah Ali Khamenei recently saying Iran "needs" 19 times more nuclear centrifuges than the amount being offered by world powers.
Meanwhile, Prime Minister Binyamin Netanyahu, who has been vocal with his opposition to the interim deal signed with Iran, scoffed Sunday at the idea that western powers should go easy on Iran's nuclear weapons program so that it will cooperate in fighting the “Islamic State (IS or ISIS).
“They are saying that the major powers need to go easy on Iran's nuclear program so that Iran will fight ISIS,” he said.
“They are fighting ISIS for their own interests. They are fighting over who will be the ruler of the Islamist world that they want to set over the entire world. It is as if Assad would say 'Go easy on my chemical weapons. Give me back my chemical weapons so that I can fight ISIS.' Both are absurd,” added Netanyahu.