U.S. Vice President JD Vance arrived in Switzerland on Sunday for peace talks with Iran as both nations seek a durable end to their war while disagreeing over Iran’s claims that it had closed the vital Strait of Hormuz.

The U.S. and Iran had agreed to a 60-day ceasefire for the negotiations, but Tehran’s Islamic Revolutionary Guard Corps on Saturday declared the Strait of Hormuz shut in response to Israeli strikes in Lebanon, although the U.S. military said commercial vessels kept operating.

Those ​developments could complicate the talks in which both sides want to advance an interim deal brokered by Pakistan and signed on Wednesday by Presidents Donald Trump and Masoud Pezeshkian ‌to end ‌an almost 4-month-long war.