By Parisa Hafezi, Francois Murphy and John Irish
VIENNA (Reuters) - Talks to revive Iran's 2015 nuclear deal with world powers were mired in uncertainty on Sunday following Russia's demands for a U.S. guarantee that the sanctions it faces over the Ukraine conflict will not hurt its trade with Tehran.
Moscow threw the potential spanner in the works on Saturday, just as months of indirect talks between Tehran and Washington in Vienna appeared to be headed for an agreement, with Foreign Minister Sergei Lavrov saying the Western sanctions over Ukraine had become a stumbling block for the nuclear deal.
U.S. Secretary of State Antony Blinken sought to dispel talk of such obstacles on Sunday when he said that the sanctions imposed on Russia over Ukraine had nothing to do with a potential nuclear deal with Iran.
"These things are totally different and just are not, in any way, linked together. So I think that's irrelevant," Blinken said in an interview with CBS's "Face the Nation" show. He added that a potential deal with Iran was close, but cautioned that a couple of very challenging remaining issues were unresolved.
Yet a senior Iranian official told Reuters earlier that Tehran was waiting for clarification from Moscow about the comments from Lavrov, who said Russia wanted a written U.S. guarantee that Russia's trade, investment and military-technical cooperation with Iran would not be hindered in any way by the sanctions.
"It is necessary to understand clearly what Moscow wants. If what they demand is related to the JCPOA, it would not be difficult to find a solution for it," said the Iranian official, referring to the 2015 nuclear deal, the Joint Comprehensive Plan of Action.
"But it will be complicated, if the guarantees that Moscow has demanded, are beyond the JCPOA."
British, French and German diplomats who had flown home before Lavrov's comments to brief officials on the nuclear talks have not indicated when they might return to Vienna.
Henry Rome, Iran analyst at consultancy Eurasia group, said reviving the nuclear pact without Russia was "tricky but probably doable, at least in the near term".
"If Russia continues to obstruct the talks, I think the other parties and Iran will have no choice but to think creatively about ways to get the deal done without Moscow's involvement," Rome told Reuters.
On Sunday, Iranian negotiators met EU diplomat Enrique Mora, who coordinates the talks between Tehran and world powers.
PRISONERS DILEMMA
Since the election of Iran's hardline president Ebrahim Raisi last year, senior officials have been pushing for deeper ties with Russia.
Iran's top authority, Supreme Leader Ayatollah Khamenei, has publicly and privately been calling for closer ties with Russia due to his deep mistrust of the United States.
The 2015 agreement, between Iran and the United States, France, Britain, Germany, Russia and Chin, eased sanctions on Tehran in return for limiting Iran's enrichment of uranium, making it harder for Tehran to develop material for nuclear weapons. The accord fell apart after President Donald Trump withdrew the United States in 2018.
The return of Iranian oil would help replace Russian barrels lost as the United States and its allies seeks to freeze out Moscow ,following the invasion and soften the impact on the West which is already struggling with high inflation.
U.S. negotiator Robert Malley has suggested that securing the nuclear pact is unlikely unless Tehran frees four U.S. citizens, including Iranian-American father and son Baquer and Siamak Namazi.
A senior Iranian official in Tehran said if Tehran's demands are met the prisoners issue can be resolved with or without a revival of the nuclear deal.
Iran, which does not recognise dual nationality, denies U.S. accusations that it takes prisoners to gain diplomatic leverage. In recent years, the elite Revolutionary Guards have arrested dozens of dual nationals and foreigners, mostly on espionage and security-related charges.
Tehran has sought the release of over a dozen Iranians in the United States, including seven Iranian-American dual nationals, two Iranians with permanent U.S. residency and four Iranian citizens with no legal status in the United States.