The United States and Iran resumed on Saturday high-stakes talks on Tehran's nuclear programme, a week after an initial round of discussions that both sides described as "constructive."

Iranian state television reported that the Oman-mediated talks in Rome began at around 0930 GMT.

Images broadcast early on Saturday by state television showed Iranian Foreign Minister Abbas Araghchi arriving in the Italian capital, where US Middle East envoy Steve Witkoff was also set to participate in the talks.

The meeting comes a week after the two sides conducted what Iran called indirect talks in Muscat. Those were the first discussions at such a high level between the foes since US President Donald Trump abandoned a landmark nuclear accord in 2018.

Western countries, including the United States, have long accused Iran of seeking to acquire nuclear weapons – an allegation Tehran has consistently denied, insisting that its programme is for peaceful civilian purposes.

Tehran and Washington have had no diplomatic relations since shortly after Iran's 1979 Islamic revolution.

Following his return to office in January, Trump revived his "maximum pressure" campaign of sanctions against Iran.

In March he sent a letter to Iran's supreme leader, Ayatollah Ali Khamenei, urging renewed nuclear talks while warning of military action if diplomacy failed.

"I'm not in a rush" to use the military option, Trump said on Thursday. "I think Iran wants to talk."

On Friday, Araghchi said Iran "observed a degree of seriousness" on the US side during the first round but questioned their intentions.

"Although we have serious doubts about the intentions and motivations of the American side, in any case we will participate in tomorrow's (Saturday's) negotiations," he said at a press conference in Moscow.

In a social media post early on Saturday, Iranian foreign ministry spokesman Esmaeil Baqaei said Tehran was "aware that it is not a smooth path, but we take every step with open eyes, relying also on past experiences." (AFP)