Flags flutter in the wind in front of the headquarters of the International Atomic Energy Agency (IAEA) in Vienna, Austria, December 16, 2020. Photo: REUTERS/Lisi Niesner

Iran and the United States will begin indirect talks in Vienna on Tuesday aimed at bringing both countries back into full compliance with the 2015 nuclear deal that Washington left three years ago.

Iran has steadily breached the accord’s limits on its nuclear program in response to Washington’s withdrawal from the accord in 2018 and its reimposition of economic sanctions.

While Tehran has repeatedly rebuffed “direct and indirect negotiations” with the US, Washington said on Monday it expected the talks to be difficult. Both Tehran and Washington did not foresee any early breakthrough.

“We are not optimistic nor pessimistic about the outcome of this meeting now, but we are confident that we are on the right track, and 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,” Iranian government spokesman Ali Rabiei told reporters.

US and Iranian officials will begin indirect talks in the Austrian capital, where the pact was originally reached in 2015, later on Tuesday. Officials from Britain, France and Germany, are expected to act as intermediaries. Russia and China, the other parties to the 2015 pact, will also attend.

A Western diplomat told Reuters on Friday that a shuttle-diplomacy approach would be adopted. The diplomat said France would be the main interlocutor for both sides.

According to diplomats, the remaining parties to the deal will first meet at a Viennese hotel for preparatory talks. The US delegation, headed by special envoy Rob Malley, will be based in a nearby hotel.

Adding fresh doubt to chances of a breakthrough, an Iranian official told Reuters: “Our agenda during the meeting will be removal of all US sanctions against Iran … as our supreme leader has said repeatedly, anything less than that will not be accepted by Tehran.”

Iran’s Supreme Leader Ayatollah Ali Khamenei, who has the final say on all state matters, has opposed any gradual easing of sanctions.

An EU official said working groups would be created with the aim of marrying lists of sanctions that the United States could lift and nuclear obligations that Iran should meet.

Diplomats said Tuesday’s talks could continue for several days to resolve some of the easier issues before resuming next week. The aim is some form of a deal ahead of June’s Iranian presidential election, the official said, although Iranian and US officials have said there is no rush.

President Joe Biden’s administration wants to revive the accord but has said that this requires negotiations. Tehran has dismissed any engagement in talks with Washington about both sides resuming compliance with the deal.

Under the 2015 accord, US and other economic sanctions on Tehran were removed in return for curbs on Iran’s nuclear program to make it harder to develop a nuclear weapon — an ambition Tehran denies.