US President Donald Trump said Sunday that Iran wanted to “negotiate” even as he suggested that military action remained an option.

“A meeting is being set up … They want to negotiate,” Trump said, but warned: “We may have to act before a meeting.”

But what would negotiations involve?

There were several rounds of indirect talks in the first half of last year between Iranian Foreign Minister Abbas Araghchi and Trump’s envoy Steve Witkoff on limits to Iran’s nuclear program, focusing on enrichment of its uranium stockpile.

The US also insisted on discussing Iran’s ballistic missile program, a demand Tehran rejected, arguing that placing limits on its missiles would leave it defenseless.

That position may have hardened after the summer’s Israeli-American attack on Iran.

The last round of US-Iran talks – in May – was described as professional and constructive by both sides, but negotiations ended abruptly when Israel launched a surprise attack on Iran in June, and the US bombed several Iranian nuclear facilities.

At the time, Trump said Iran’s nuclear program had been obliterated. Other assessments suggested it had been put back months or maybe years, but not destroyed.

Iran has said it is willing to return to talks but won’t give up on enrichment of uranium, a nuclear fuel that can be used to build a bomb if refined to high levels.

“Figuring out the path to a deal is not rocket science,” Araghchi posted in May.

“Zero nuclear weapons = we DO have a deal. Zero enrichment = we do NOT have a deal.”

In an interview with CNN in November, Kamal Kharrazi, foreign policy adviser to Supreme Leader Ayatollah Ali Khamenei, said the US would have to initiate a resumption of talks.

“They have to make the first move to show that they are ready to engage with us on the conditions that we put… it has to be based on equal footing and mutual respect,” he said in November.