Iran and the United States prepared on Saturday to start in-depth negotiations in Oman over Tehran's rapidly advancing nuclear program, talks that likely will hinge on the Islamic Republic's enrichment of uranium.

Iranian state television suggested the talks could start mid-day on Saturday in Muscat, the mountain-wrapped capital of this sultanate on the eastern edge of the Arabian Peninsula.

However, neither Iranian Foreign Minister Abbas Araghchi nor US Mideast envoy Steve Witkoff offered any immediate specifics or details on the talks that they'll lead.

Araghchi arrived on Friday in Oman and met with its Foreign Minister Badr al-Busaidi, who has mediated the two previous round of talks in Muscat and Rome.

Araghchi then visited the Muscat International Book Fair, surrounded by television cameras and photojournalists. Late Saturday morning footage showed Araghchi heading for the talks.

Witkoff was in Moscow on Friday meeting Russian President Vladimir Putin.

He arrived on Saturday in Oman, where the talks were expected to start in the coming hours, a source familiar said.

The talks seek to limit Iran’s nuclear program in exchange for the lifting of some of the crushing economic sanctions the United States has imposed on the Islamic Republic closing in on half a century of enmity .

US President Donald Trump has repeatedly threatened to unleash airstrikes targeting Iran’s program if a deal isn’t reached.

Iranian officials increasingly warn that they could pursue a nuclear weapon with their stockpile of uranium enriched to near weapons-grade levels.

Iran's 2015 nuclear deal with world powers did limit Tehran's program.

However, Trump unilaterally withdrew from it in 2018, setting in motion years of attacks and tensions.

The wider Middle East also remains on edge over the devastating Israel-Hamas war in the Gaza Strip .

Trump, traveling to Rome for the funeral of Pope Francis, again said he hoped negotiations would lead to a new nuclear deal. However, he still held out the possibility of a military strike if they didn't.

“The Iran situation is coming out very well,” Trump said on Air Force One.

“We've had a lot of talks with them and I think we're going to have a deal. I'd much rather have a deal than the other alternative. That would be good for humanity."

He added: “There are some people that want to make a different kind of a deal – a much nastier deal – and I don’t want that to happen to Iran if we can avoid it.”

While Araghchi and Witkoff are again expected to speak through the Omanis, experts on both sides also will begin negotiating details of a possible deal.

From the Iranian side, Iranian Deputy Foreign Minister Majid Takht-e Ravanchi will lead Tehran’s expert team.

The US technical team will be led by Michael Anton, the director of Secretary of State Marco Rubio’s policy planning staff. Anton does not have the nuclear policy experience of those who led America’s efforts in the 2015 talks. (AP)