Iranian Foreign Minister Abbas Araghchi and US Middle East envoy Steve Witkoff will hold the Oman-mediated talks in Rome.
They come one week after the two sides held what Iran called indirect talks in Muscat. Those were the first talks 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 fails.
"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.
"we will participate in tomorrow's (Saturday) negotiations," he said at a press conference in Moscow.