Iran's chief nuclear negotiator said on Saturday Tehran expects US sanctions on oil, banks and most individuals and institutions to be lifted based on agreements so far in Vienna talks, Iranian media reported, while Washington again played down the prospect of an imminent breakthrough. 

Russia and Western European powers meanwhile gave contrasting accounts of the task ahead in the talks to bring Iran and the United States fully back into compliance with a 2015 nuclear deal, as the talks adjourned for six days.

"Sanctions ... on Iran's energy sector, which include oil and gas, or those on the automotive industry, financial, banking and port sanctions, all should be lifted based on agreements reached so far," Deputy Foreign Minister Abbas Araqchi was quoted as saying by Iranian state media.

Araqchi did not say under which mechanism sanctions would be lifted or refer to how Tehran would meet Washington's demands and return to its commitments under the deal.

"We will negotiate until the two sides' positions come closer and our demands are met," he said. "If they are met there will be an agreement, if not there will naturally be no agreement."

Asked to comment, the US State Department referred back to past statements, including remarks on Friday from the US national security adviser, Jake Sullivan, who said the talks were in "an unclear place."

"We've seen willingness of all sides, including the Iranians, to talk seriously about sanctions relief restrictions and a pathway back into the JCPOA," Sullivan said. "But it is still uncertain as to whether this will culminate in a deal in Vienna," he said.