Iranian state television reported the talks had begun in Muscat, the mountain-wrapped capital of this sultanate on the eastern edge of the Arabian Peninsula. A person close to U.S. Mideast envoy Steve Witkoff, speaking on condition of anonymity to discuss the closed-door talks, also acknowledged the meeting had started.

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

Araghchi arrived Friday in Oman and met with Omani 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. Video late Saturday morning showed Araghchi heading to the talks.

Witkoff was in Moscow on Friday meeting Russian President Vladimir Putin. He arrived Saturday to Oman, where the talks were expected to start in the coming hours, a source familiar with Witkoff’s travels told The Associated Press, speaking on condition of anonymity to discuss the closed-door negotiations.

Meanwhile Saturday, a massive explosion rocked a port in southern Iran just after the talks began, injuring at least 516 people. Authorities offered no immediate cause for the blast, which appeared to have been caused by a highly combustible material — though officials ruled out its oil and gas industry.

Nuclear talks come after decades of tensions

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

U.S. 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.”

Talks turn to experts

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, said Mohammad Golzari, an Iranian government official. Takht-e Ravanchi took part in the 2015 nuclear talks.

The U.S. technical team, which is expected to arrive in Oman on Friday, will be led by Michael Anton, the director of U.S. 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.

Iran has insisted that keeping its enrichment is key. But Witkoff has muddied the issue by first suggesting in a television interview that Iran could enrich uranium at 3.67%, then later saying that all enrichment must stop. That demand all enrichment stop also has been repeated by U.S. Secretary of State Marco Rubio.

However, Iranians remain hopeful the talks could be successful, as the Iranian rial has rebounded from historic lows during which it took over 1 million rial to buy $1.

“It’s OK to negotiate, to make the nuclear program smaller or bigger, and reach a deal,” Tehran resident Farzin Keivan said. “Of course we shouldn’t give them everything. After all, we’ve suffered a lot for this program.”