Iran and the United States began a fourth round of negotiations on Sunday over Tehran’s rapidly advancing nuclear programme, officials said, just ahead of a visit by President Donald Trump to the Middle East this week.

The round of talks, again happening in the sultanate of Oman, likely will see Oman’s Foreign Minister Badr al-Busaidi mediating. American officials believe the talks will include both indirect and direct portions, as in previous rounds of negotiations, but like the other rounds in Muscat and Rome, details remain scarce.