Storyline: A fourth round of indirect nuclear talks between Iran and the United States concluded in Oman on Sunday, with the Iranian Ministry of Foreign Affairs describing the three-hour talks as "difficult but useful" while the key issue around Iran's uranium enrichment program remains. The talks in Muscat, mediated by Oman, mark the latest effort to salvage the Joint Comprehensive Plan of Action. The plan was drawn up back in 2015 but thrown into doubt after United States unilaterally withdrew from the accord in 2018 under U.S. President Donald Trump's first term, prompting Iran to gradually reduce its compliance with the nuclear commitments set out in the plan. Iranian Foreign Ministry spokesman Esmaeil Baghaei said on Sunday that the fourth round of indirect Iran-U.S. negotiations had proven "difficult but useful" in helping to better understand each other's positions and find reasonable and realistic ways to address their differences. Following the talks, Iranian Foreign Minister Abbas Araqchi said the indirect negotiations with the U.S. had been much more serious and frank, as the discussions had shifted from general topics to more specific proposals. He characterized the talks as "forward-moving" but acknowledged the growing complexity of the related issues. The latest round of talks headed by Araghchi and U.S. Special Envoy to the Middle East Steve Witkoff, lasted for about three hours, and follows previous sessions held in Muscat on April 12 and 26, as well as a meeting in Rome on April 19. Speaking on condition of anonymity, a senior Trump administration official said the U.S. side was encouraged by Sunday's outcome and looks forward to their next meeting which is expected in the near future. An agreement was reached to move forward with the talks, which will continue working through technical elements, the official said. Omani Foreign Minister Badr Albusaidi said in a social media post that the talks included "useful and original" ideas that reflected a shared wish to reach an "honorable" agreement between Iran and the U.S., adding that the next round of talks will take place once both sides have consulted with their leaders. No specific date has been agreed for the next round which will be announced by mediator Oman in due course, according to media reports. Iran insists that its right to maintain uranium enrichment for peaceful purposes is non-negotiable, while the United States says all related nuclear infrastructure must be dismantled, raising concerns that this issue could become a major obstacle to negotiations. Shotlist: FILE: Muscat, Oman - Feb 23, 2025: 1. Oman's Foreign Ministry building, national flag of Oman FILE: Muscat, Oman - Date Unknown: 2. Sultan Qaboos Grand Mosque FILE: Tehran, Iran - April 10, 2023: 3. National flag of Iran, city view, traffic FILE: Tehran, Iran - March 2024: 4. Various of Azadi Tower FILE: Iran - Date Unknown: 5. Various of traffic, national flags of Iran FILE: Washington D.C., USA - October 2024: 6. Various of White House 7. Various of Capitol building, U.S. national flag FILE: New York, USA - October 2024: 8. Various of traffic 9. City view. [Restrictions: No access Chinese mainland/Al-Arabiya/Persian language TV Stations outside Iran. Strictly No Access BBC Persian/VOA Persian/Manoto TV/Iran International TV]