Talks on reviving the Iran nuclear deal moved forward in Vienna on Tuesday with diplomats preparing to draw up “concrete measures” the US and Iran could take.
The EU said a meeting between Iran and the remaining parties to the deal – Britain, France, Germany, Russia and China – had been “constructive” and ended with “unity and ambition” towards salvaging the agreement.
A US delegation was based at another hotel in the Austrian capital, with European diplomats acting as mediators between Washington and Tehran.
Earlier on Tuesday, Iran welcomed "promising" signs that Joe Biden's administration was willing to lift sanctions reimposed by Donald Trump in 2018.
Two expert groups are now set to hold further talks in Vienna about a possible US return to the deal.
“There’s unity and ambition for a joint diplomatic process with two expert groups on nuclear implementation and sanctions lifting,” said Enrique Mora, the deputy secretary-general of the EU External Action Service.
“As co-ordinator I will intensify separate contacts here in Vienna with all separate parties, including the US,” he said.
Mikhail Ulyanov, Russia’s envoy to the UN’s International Atomic Energy Authority, said the main talks at Vienna’s Grand Hotel had been successful.
The two expert groups must “identify concrete measures to be taken by Washington and Tehran to restore full implementation” of the deal, he said.
Mr Ulyanov said the restoration of the Joint Comprehensive Plan of Action would not happen immediately.
“It will take some time. How long? Nobody knows,” he said.
“The most important thing after today’s meeting of the Joint Commission is that practical work towards achieving this goal has started.”
Robert Malley, a special US envoy for Iran who is leading Washington’s delegation on the sidelines of the summit, told broadcaster PBS before the talks that “the United States knows that, in order to get back into compliance, it’s going to have to lift those sanctions that are inconsistent with the deal”.
Asked to respond to Mr Malley’s remarks, Iranian government spokesman Ali Rabiei told reporters earlier on Tuesday: “We salute these comments.”
“We find this position realistic and promising. It could be the start of correcting the bad process that had taken diplomacy to a dead end,” Mr Rabiei said.
He said Iran was “not optimistic nor pessimistic about the outcome of this meeting”, but that Tehran was “confident that we are on the right track”.
“If America’s will, seriousness and honesty is proven, it could be a good sign for a better future for this agreement and ultimately its full implementation,” he said.
Iran’s deputy foreign minister, Abbas Araqchi, is leading Tehran’s delegation to the talks, which includes representatives from the Central Bank of Iran, the country’s oil ministry and the Atomic Energy Organisation of Iran.
Diplomats said the talks could continue for several days to resolve some of the easier issues before resuming next week.
France was expected to be the main interlocutor for both sides, a western diplomat told Reuters.
The US left the pact under president Donald Trump in 2018 and reimposed sanctions on Iran under what Washington called a “maximum pressure” campaign.
Since then, Iran has steadily flouted the restrictions it agreed to under the deal, including the amount of enriched uranium it can stockpile.
The restrictions under the 2015 pact were intended to make it harder to develop a nuclear weapon, although Tehran denies seeking to develop atomic bombs.
Joe Biden’s administration said it wants both sides to resume compliance with the pact.
US President Joe Biden has said he is ready to reverse the decision of his predecessor Donald Trump to withdraw from the landmark 2015 agreement, negotiated to ensure that Iran never developed a military nuclear programme.
"We do see this as a constructive and certainly welcome step," US State Department spokesman Ned Price said of the talks a little later.
"It is a potentially useful step as we seek to determine what it is that the Iranians are prepared to do to return to compliance with the stringent limitations under the 2015 deal, and as a result what we might need to do to return to compliance ourselves," he added.
Tehran is demanding an end to the crippling sanctions Trump imposed - before which Iran will not meet the US delegates.
But Mr Biden also faces calls to tie the lifting of sanctions to the release of foreign "hostages" in Iran.
On the eve of the Vienna talks, a German-Iranian woman, Nahid Taghavi, was returned to solitary confinement in Tehran in what her family believes was a move intended to put pressure on Berlin, a signatory to the pact.
Iran’s Foreign Ministry said on Saturday that it wants the US to lift all the sanctions and rejects any “step by step” easing of restrictions.
“Robert Malley will have to leave Vienna empty-handed if the Tuesday meeting would result in anything other than the removal of all US sanctions,” a source close to Tehran’s negotiating team told the Iranian state-controlled Press TV on Monday.
Kelsey Davenport, director for nonproliferation policy at the Arms Control Association think tank, said the lack of direct Iran-US talks was not ideal but the EU was well placed to break the stalemate.
She called for a “bold first step by both sides” which she hoped would inject “much-needed momentum” into the process.
France’s Foreign Minister Jean-Yves Le Drian had urged Iran to “be constructive in the forthcoming discussions” after speaking to his counterpart Javad Zarif on Saturday.
Mr Le Drian also “called on Iran to refrain from any further violation of its current nuclear commitments which is likely to undermine the momentum for resuming discussions”.