A member of the Iranian delegation to the nuclear talks says the Ukraine war will eventually force Washington to agree to Tehran's demands and make a deal.

"Failure to reach a deal [so far] is a result of domestic troubles in the US but the ever-increasing problems caused by the Ukraine war will put pressure on [President Joe] Biden to accept the necessity of a deal [with Tehran]," Mohammad Marandi, the US-born media advisor of the Iranian delegation to the Vienna nuclear talks told the official news agency IRNA on Sunday.

Marandi claimed that none of the other parties in the talks -- the three European sides, Russia, China and Tehran -- have any problem with continuing the talks. "It has to be seen what decision Biden will make about continuing [the negotiations]," he said.

Marandi who is often interviewed as a commentator on Iran's foreign relations by the state media told IRNA that Americans admit Iran has scored 'considerable gains' in the talks. "That's why some of the members of the US delegation resigned and left the teas in protest," he said referring to the resignation of Richard Nephew, the architect of Washington's sanctions on Iran in January, and part-time senior adviser Dan Shapiro in March.

"Talks were progressing fast during the last few days but the Americans abruptly put a break to them over various issues including the lifting of sanctions and its verification, guarantees, as well as [delisting of the] IRGC," Marandi said.

Tehran insists that the designation of the IRGC as a terrorist organization was part of the Trump administration's 'maximum pressure' campaign against Iran and therefore should be reversed, but the US considers the designation unrelated to the nuclear issue.

Iranian officials reiterate that it is Washington's "excessive demands" that has prevented a deal from materializing and that Tehran will not surrender to such demands.

What the US state department has said is that if Iran wishes to discuss sanction unrelated to the nuclear issue, it should accept to widen the talks to include other outstanding problems.

Pundits now consider a deal to restore the 2015 deal, Joint Comprehensive Plan of Action (JCPOA), much less likely than in mid-March when it appeared to be only a few days away, as Tehran and Washington both insist on their positions and throwing the onus on each other.

"Chances of a deal and the restoration of the JCPOA are less than a few months ago. For any progress either the US or the Iranian side must make a compromise. It's quite possible that failing to do so could prevent a deal from being made," Karl Kaltenhaler, director of the Center for Intelligence and Security Studies at The University of Akron in Ohio told the Iranian Labour News Agency (ILNA) Thursday.

In an interview with London-based The New Arab newspaper published Friday, the US ambassador to the UN Linda Thomas-Greenfield said there was a possibility that there will not be an agreement over the restoration of the JCPOA and mutual compliance. "We're ready and they're not," she said.

She also reiterated that the Biden administration would work to ensure that Iran is never allowed to acquire nuclear weapons, suggesting that the US will use its vote, if the matter is referred to the UN Security Council, to put the brakes on Iran's nuclear program.