DUBAI, United Arab Emirates >> Iran and the United States held a fourth round of negotiations Sunday over Tehran’s rapidly advancing nuclear program, just ahead of a visit by President Donald Trump to the Middle East this week.

The talks ran for some three hours in Muscat, the capital of Oman, which has been mediating the negotiations, said a U.S. official. Iranian Foreign Ministry spokesperson Esmail Baghaei also said the talks took place that long and that a decision on the next round of talks is under discussion.

Baghaei called the talks “difficult but useful.” The U.S. official, speaking on condition of anonymity to discuss the closed-door negotiations, offered a little bit more, describing them as being both indirect and direct.

“Agreement was reached to move forward with the talks to continue working through technical elements,” the U.S. official said. “We are encouraged by today’s outcome and look forward to our next meeting, which will happen in the near future.”

Iran insisted they only took place indirectly — possibly over internal political pressures within the Islamic Republic.

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.

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. Meanwhile, Israel has threatened to strike Iran’s nuclear facilities on their own if it feels threatened, further complicating tensions in the Mideast already spiked by the Israel-Hamas war in the Gaza Strip.

The fourth round comes ahead of Trump’s trip

The talks again saw Iranian Foreign Minister Abbas Araghchi and U.S. Mideast envoy Steve Witkoff lead the negotiations. They have met and spoken face-to-face but the majority of the negotiations appear to have been indirect, with Omani Foreign Minister Badr al-Busaidi shuttling messages between the two sides.

“The discussions included useful and original ideas reflecting a shared wish to reach an honorable agreement,” al-Busaidi wrote afterward on the social platform X.

Iran has insisted that keeping its ability to enrich uranium is a red line for its theocracy, with Araghchi before the talks describing Iran’s program as springing from “the blood of our nuclear scientists.” Israel is widely suspected of carrying out assassinations targeting the program’s scientists.

“From our viewpoint, enrichment is a subject that should definitely continue and there is no room for compromise on that,” Araghchi told Iranian state television after the talks. “It is possible that we consider some limits on its dimensions, amount and level for trust building, similar to the past.”

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.

“An enrichment program can never exist in the state of Iran ever again,” Witkoff told the right-wing Breitbart news site in a piece published Friday. “That’s our red line. No enrichment. That means dismantlement, it means no weaponization, and it means that Natanz, Fordow, and Isfahan — those are their three enrichment facilities — have to be dismantled.”