United States and Iranian representatives met in Muscat, the capital of Oman, for negotiations regarding the future of Tehran’s nuclear program after a U.S.-mediated ceasefire ended a 12-day conflict last summer, marking the first face-to-face summit since the war.

The U.S. State Department has issued a warning urging American citizens to leave Iran immediately due to worsening security conditions, citing a list of open border crossings.