An alleged sabotage attack on Iranian nuclear facilities will make it harder for diplomats to strike a deal as they look to rescue Iran's 2015 agreement with world powers, an expert says.
Talks on a possible US return to the nuclear deal are due to resume in Vienna on Thursday but are being overshadowed by the incident at the Natanz plant and Iran's subsequent announcement that it would enrich uranium up to 60 per cent.
Eric Brewer, a senior fellow at the Centre for Strategic and International Studies, said on Tuesday the path to an agreement "has only got tougher in the past 48 hours".
In an article for the Royal United Services Institute (Rusi), he said the "tough negotiations", in which European powers have shuttled between the Iranians and a US delegation, are "by no means guaranteed to succeed".
Mr Brewer said it was hard to see how Washington would agree to Iran's demands for the lifting of sanctions to be followed by a verification period before Tehran will accept limits on its nuclear activity.
"Iran has suggested that verifying sanctions removal could include steps such as successfully exporting oil, signing new oil contracts and conducting financial transactions through multiple channels," he said.
"A symbolic delivery of oil is one thing, but waiting for Iran to sign ... new contracts is quite another."
Diplomats in Vienna asked two expert groups to work out how sanctions can be lifted and how Iran can move back in line with the nuclear limits under the deal.
Mr Brewer said the nuclear side of the deal would probably be "easier to work out and less contentious than the sanctions rollback".
But he added that "it is hard to know for sure given that the US and Iran have yet to meet to dig into the details and Washington has not spoken much in public about its objective".
Iran struck the deal with the US, Britain, France, Germany, Russia and China in 2015, but Washington pulled out in 2018 and re-imposed sanctions.
Joe Biden's administration is working towards restoring the deal but the talks are expected to last months.
"It remains to be seen whether the parties can build on the constructive start in Vienna," Mr Brewer said.
"The recent sabotage efforts against Iran’s main enrichment facility will probably make that harder in the short term.
"The US and the remaining parties to the deal will get a better sense this week of whether Iran’s positions are ‘red lines’ or ‘pink lines’."
Russia's ambassador to the International Atomic Energy Agency, Mikhail Ulyanov, said on Tuesday that the next round of talks in Vienna had been postponed until Thursday.
"No doubt that in addition to previous issues the Commission will address the latest steps of Iran in the nuclear field, including 60 per cent enrichment," Mr Ulyanov said.
The United States, which denies any involvement in the Natanz incident, said it was "certainly concerned about these provocative announcements" by Iran.
However, Washington said it expects the talks in Vienna to continue.
"We expect and we have not been alerted of any change in planned attendance in meetings that will resume later this week," said White House press secretary Jen Psaki.
Announcing the 60 per cent enrichment, Iran's chief nuclear negotiator Abbas Araqchi also said Iran would activate 1,000 advanced centrifuge machines at Natanz.
One of the central objectives of the 2015 deal was to extend the time Iran would need to accumulate enough enriched uranium to build a nuclear weapon.
Iran insists it has never sought to obtain or develop nuclear weapons, and that its nuclear technology is for civilian purposes only.
