Iran and the United States will hold a new round of nuclear talks in Rome on Saturday to resolve their decades-long standoff over Tehran’s atomic aims, under the shadow of President Donald Trump’s threat to unleash military action if diplomacy fails.

Iran’s Foreign Minister Abbas Araqchi and Trump’s Middle East envoy Steve Witkoff will negotiate indirectly through mediators from Oman, a week after a first round in Muscat that both sides described as constructive.

Araqchi has arrived in Rome to attend the second round of the talks, according to a post on his Telegram account. He said in Moscow on Friday that Iran believes reaching an agreement on its nuclear programme with the United States is possible as long as Washington is realistic.

Tehran has however sought to tamp down expectations of a quick deal, after some Iranian officials speculated that sanctions could be lifted soon. Iran’s utmost authority, Supreme Leader Ayatollah Ali Khamenei, said this week he was “neither overly optimistic nor pessimistic”.

For his part, Trump told reporters on Friday: “I’m for stopping Iran, very simply, from having a nuclear weapon. They can’t have a nuclear weapon. I want Iran to be great and prosperous and terrific.”

Trump, who ditched a 2015 nuclear pact between Iran and six powers during his first term in 2018 and reimposed crippling sanctions on Tehran, has revived his “maximum pressure” campaign on Iran since returning to the White House in January.

Washington wants Iran to halt production of highly enriched uranium, which it believes is aimed at building an atomic bomb.

Tehran, which has always said its nuclear programme is peaceful, says it is willing to negotiate some curbs in return for the lifting of sanctions, but wants watertight guarantees that Washington will not renege again as Trump did in 2018.

Since 2019, Iran has breached and far surpassed the 2015 deal’s limits on its uranium enrichment, producing stocks far above what the West says is necessary for a civilian energy programme.

A senior Iranian official, who described Iran’s negotiating position on condition of anonymity, listed Iran’s red lines as never agreeing to dismantle its uranium enriching centrifuges, halt enrichment altogether or reduce its enriched uranium stockpile below levels agreed in the 2015 deal. Iran also rejects negotiating about defence capabilities such as missiles.

While both Tehran and Washington have said they are set on pursuing diplomacy, there is still a wide gap between them on the dispute that has rumbled on for more than two decades.

Witkoff and Araqchi interacted briefly at the end of the first round last week, but officials from the two countries have not held direct negotiations since 2015, and Iran said the Rome talks would also be held indirectly through the Omani mediators.

Russia, a party to Iran’s 2015 nuclear agreement, has offered “to assist, mediate, and play any role” that will be beneficial to Iran and the United States.