- Iran confirmed in January it was enriching uranium to 20 percent purity, well beyond the threshold set by the deal.
VIENNA: The United States is set to start talks with EU negotiators on Tuesday in Austria's capital Vienna aimed at salvaging an international agreement on Iran's nuclear programme, which Washington withdrew from in 2018.
US President Joe Biden has said he is ready to reverse the decision of his predecessor Donald Trump and return to the 2015 agreement, which was supposed to ensure that Iran never developed a military nuclear programme.
But Iran is demanding an end to crippling sanctions imposed by Trump and has refused to meet US negotiators at the latest talks, meaning European players will act as intermediaries.
Ahead of the talks, US special envoy Rob Malley suggested that the United States could be open to lifting sanctions and returning to the 2015 deal, comments Iran government spokesman Ali Rabiei called "promising".
"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," he told reporters in Tehran on Tuesday.
Iran confirmed in January it was enriching uranium to 20 percent purity, well beyond the threshold set by the deal.
Ali Vaez of the International Crisis Group, which monitors conflicts, tweeted that the talks represented "an important marker that both U.S. & Iran are serious about breaking the inertia".
Since neither side appears willing to take the first step, experts such as Vaez have suggested the negotiators could make a "gesture-for-gesture" deal to break the deadlock.
Rabiei reiterated Iran was ready to reverse the steps it had taken as soon as all sanctions imposed during the Trump administration are lifted.
"We do not accept a step by step approach," he said.
The European Union will preside over talks between current members of the 2015 pact -- Iran, China, France, Germany, Russia and Britain -- set to take place later on Tuesday at a luxury hotel.
"Preparatory bilateral meetings are under way," Mikhail Ulyanov, Russia's Vienna-based envoy to international organisations, wrote on Twitter.
The US delegation will meet in a different hotel with EU negotiators acting as go-betweens.
At the same time, expert meetings are expected to take place and could take "15 days, a month, we don't know", according to a Vienna-based diplomat. US delegates are not part of those meetings, but will be updated.
Kelsey Davenport, director for Non-proliferation Policy at the Arms Control Association think-tank, said the lack of direct Iran-US talks was not ideal but added that the EU was well situated 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.
Washington, for example, could unfreeze Iranian funds held in foreign banks and facilitate humanitarian trade, and Tehran could stop enriching uranium beyond the levels agreed in the 2015 accord, said Davenport.
"The problem is all the irreversible things, like the research activities Tehran has undertaken," the diplomat pointed out.
On the eve of the talks, Malley, the US special envoy on Iran, talked of removing "those sanctions that are inconsistent with the deal".
"If we're realistic about what both sides have to do... we could get there," he told US broadcaster PBS.
"But if either side takes a maximalist position and says that the other side has to do everything first before it's going to move one inch, I think it's hard to see how this succeeds."