Any shippers paying tolls to Iran for passage through the Strait of Hormuz, including charitable donations to organisations such as the Iranian Red Crescent Society, are at risk of punitive sanctions, the US Treasury Department warns, according to Reuters.

The advisory, from Treasury’s Office of Foreign Assets Control (OFAC), said the US is aware of Iranian threats to shipping and demands for payments to receive safe passage through the Strait.

OFAC says demands may include several payment options, including fiat currency, digital assets, offsets, informal swaps, or other in-kind payments, such as nominally charitable donations made to the Iranian Red Crescent Society, Bonyad Mostazafan, or Iranian embassy accounts.

“OFAC is issuing this alert to warn US and non-US persons about the sanctions risks of making these payments to, or soliciting guarantees from, the Iranian regime for safe passage,” it said. “These risks exist regardless of payment method.”