The U.S. Maritime Administration has advised U.S.-flagged ships to stay “as far as possible” from Iranian waters in the Strait of Hormuz amid heightened tensions with Tehran.

Captains are instructed to refuse permission for Iranian forces to board, and if boarding occurs, crews should not forcibly resist, though this does not imply consent.

The guidance recommends eastbound ships transit near the Omani side of the strait, a key route carrying about a third of global seaborne crude oil.

The advisory follows indirect U.S.-Iran talks in Oman on Tehran’s nuclear program, described by leaders from both sides as a cautious first step, CNBC has reported.

The Strait’s strategic importance has made it a focal point amid U.S. military threats and concerns over potential disruptions to global energy markets.