The State Department Friday said US negotiator Robert Malley and his team have returned to Washington after negotiations to reach an Iran nuclear deal paused.

After 11 months of multilateral talks in Vienna diplomats have been insisting that a deal was at hand to revive the 2015 Iran nuclear agreement known as JCPOA, before Russia made last-minute demands on Saturday.

Moscow has asked for exemption from Ukraine sanctions in its economic and other relations with Iran. The US and its European allies have dismissed Russia's demand, saying sanctions imposed over the Ukraine invasion are not related to the Iran nuclear deal.

State Department spokesperson Ned Price also told reporters the United States continues to believe that a potential deal to return to the Iran nuclear agreement is close, but said decisions need to made in places like Tehran and Moscow.

Iran has been downplaying the Russian demand, claiming that Washington has not made its final decisions over the nuclear deal and has presented new demands.