By Francois Murphy
VIENNA (Reuters) -Russia and Western European powers gave contrasting accounts on Saturday of the task ahead in talks to bring Iran and the United States fully back into compliance with the 2015 nuclear deal, as the talks adjourned for six days.
The talks began last month in Vienna with the remaining parties to the deal - Iran, Russia, China, France, Britain and Germany - meeting in the basement of a luxury hotel, and the United States based in another hotel across the street. Iran has refused to hold direct meetings with U.S. officials.
President Joe Biden is seeking to return to the deal after Washington pulled out in 2018 under then President Donald Trump and reimposed sanctions against Tehran. Iran responded as of 2019 by breaching many of the deal's limits on its nuclear activities.
"We have much work, and little time, left. Against that background, we would have hoped for more progress this week," senior diplomats from the so-called E3 - France, Britain and Germany - said in a statement.
Officials have said they hope to reach a deal by May 21, when an agreement between Tehran and the U.N. nuclear watchdog on continued monitoring of some Iranian nuclear activities is due to expire.
"We have yet to come to an understanding on the most critical points. Success is by no means guaranteed, but not impossible," they added.
U.S. National Security Adviser Jake Sullivan said on Friday the talks were in "an unclear place", meaning it was uncertain whether they would lead to an agreement.
"We should not expect breakthroughs in the days to come," Russia's ambassador to the U.N. nuclear watchdog, Mikhail Ulyanov, told reporters after a meeting of the remaining parties that wrapped up the third round of talks, adding the talks would reconvene on Friday.
"We need simply to continue diplomatic, day-to-day work, and we have all the reasons to expect that the outcome, (the) final outcome, will be successful and it will come quite soon, in a few weeks," said Ulyanov, who is one of the more optimistic voices at the talks.
The break in talks was widely expected as diplomats said officials from several countries are also involved in the Group of Seven foreign ministers' meeting in London that begins on Monday and ends on Wednesday.