By John Irish and Francois Murphy
VIENNA (Reuters) - Parties trying to revive the Iran nuclear deal scrambled on Wednesday to resolve last-minute Russian demands that threaten to scupper negotiations, diplomats said, with the United States appearing unwilling to engage with Russia on the matter.
Western powers on Tuesday warned Russia against wrecking an almost completed deal on bringing the United States and Iran back into compliance with the 2015 accord. Iran's top negotiator returned to Vienna on Wednesday from consultations in Tehran.
Russia's envoy to the talks, Mikhail Ulyanov, dismissed any suggestion Moscow was holding up an agreement and said a final text had in any case not been completed.
Eleven months of talks to restore the deal, which lifted sanctions on Iran in return for curbs on its nuclear programme, have reached their final stages with several diplomats saying there was broad agreement.
But just as the final issues were being resolved, Russia presented a new obstacle by demanding written guarantees from the United States that Western sanctions targeting Moscow over its invasion of Ukraine would not affect its trade with Iran.
Ulyanov said Moscow's demands had not received a positive reaction.
"In view of the new circumstances and wave of sanctions against Russia we have the right to protect our interests in the nuclear field and wider context," Ulyanov said.
He said the United States and the European Union had to make it clear that neither now or in the future sanctions could hit the implementation of nuclear projects in Iran as well as its trade and economic relations.
Ulyanov met the coordinator of the talks, Enrique Mora of the European Union, on Tuesday evening and again on Wednesday.
He said he would still have to report back to Moscow for a final decision after the text was finalised.
"There is no final text so how can our position delay anything if final negotiations are not finished," he said.
"A number of participants at this moment are not ready to confirm that the text is fully acceptable to them."
U.S. NOT PLAYING
U.S. Under Secretary of State for Political Affairs Victoria Nuland on Tuesday accused Russia of seeking to reap extra benefits from its participation in the effort to restore the nuclear agreement, but she said Washington would not be playing "Let's Make a Deal."
Two Western diplomats said it was still not clear what the exact nature of Moscow's demands were, while a European diplomat said Russia was demanding sweeping guarantees on trade between Moscow and Tehran, demands that were deemed unacceptable.
They said the talks were now not likely to end this week.
Mora broke off informal meetings on Monday saying the time had come for political decisions to be taken to end the negotiations.
European negotiators from France, Britain, and Germany had already temporarily left the talks as they believed they had gone as far as they could go and it was now up to the United States and Iran to agree on outstanding issues.
Iran's chief negotiator, Ali Bagheri Kani, returned to Tehran unexpectedly after Russian Foreign Minister Sergei Lavrov outlined Moscow's new demands. Iran's foreign minister said at the time that Tehran would not let its interests be harmed by "foreign elements".