STRAIT OF HORMUZ — The U.S. Office of Foreign Assets Control posted an alert on Friday warning shipping companies that payments to Iran for safe passage through the Strait of Hormuz could trigger U.S. sanctions. The advisory cautioned that companies making such payments risk enforcement action under existing sanctions on Iran.

About one-fifth of the world's trade in oil and natural gas typically passes through the Strait of Hormuz at the mouth of the Persian Gulf in peacetime. Iran effectively closed the strait to normal traffic by attacking and threatening to attack ships after the U.S. and Israel launched a war on February 28. Iran later began offering some ships safe passage by detouring them through alternate routes closer to its shoreline, charging fees at times for the service.

According to the Office of Foreign Assets Control, the payment demands could include transfers not only in cash but also digital assets, offsets, informal swaps, or other in-kind payments, including charitable donations and payments at Iranian embassies. The alert applies broadly to any shipping company that moves goods through the strait and makes payments to Iranian authorities in exchange for passage, regardless of the form those payments take.