MUSCAT, Oman — Negotiations between Iran and the United States over Tehran’s rapidly advancing nuclear program will return Saturday to the secluded sultanate of Oman, where experts on both sides will start hammering the technical details of any possible deal.

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 50 years 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.

The Muscat talks come as Iran appears to have lined up Chinese and Russian support. Araghchi traveled to Moscow last week and Beijing this week.

On Thursday, Chinese, Iran and Russian representatives met the head of the International Atomic Energy Agency, the United Nations’ nuclear watchdog that likely will verify compliance with any accord like it did with Tehran’s 2015 nuclear deal with world powers. That deal included China and Russia, as well as France, Germany and the United Kingdom.

However, Iran has greatly restricted the IAEA’s inspections — leading to fears internationally that centrifuges and other nuclear material could be diverted.

The IAEA offered no readout from the talks, but China’s state-run Xinhua news agency on Friday described the three nations as saying the agency has “the necessary potential and expertise to contribute constructively to this process.”

“China, Russia and Iran emphasized that political and diplomatic engagement based on mutual respect remains the only viable and practical path for resolving the Iran nuclear issue,” the report said. It added that China respects Iran’s “right to the peaceful use of nuclear energy.”

The Trump administration has kept France, Germany and the U.K. out of its direct negotiations with Iran, similarly reflected in Witkoff’s negotiations with Russia over ending its war on Ukraine. Witkoff traveled Friday to Moscow ahead of Saturday’s meeting in Muscat.