US issues urgent warning for Strait of Hormuz amid Iranian tension

The warning comes just days after the most recent incident on February 3, when Iranian forces reportedly attempted to force commercial vessels into Iranian territorial waters. Iranian forces have historically used small boats and helicopters to conduct boarding operations against merchant shipping in the region, according to the advisory.

The US Government is "continually assessing the maritime security situation in the region to identify and differentiate threats and safeguard freedom of navigation," the advisory states.

The advisory provides step-by-step instructions for vessel masters confronted by Iranian forces. If hailed, vessels should provide their name and flag state while affirming they are "proceeding in accordance with international law as reflected in the Law of the Sea Convention."

Crucially, the guidance instructs masters to "decline permission to board" if it is safe to do so. However, if Iranian forces do board, crew members "should not forcibly resist" — though the advisory stresses that refraining from resistance "does not imply consent or agreement to that boarding."

U.S.-flagged vessels are advised to remain "as far as possible from Iran's territorial sea without compromising navigational safety." When transiting eastbound through the narrow Strait of Hormuz, ships are encouraged to stay close to Omani waters.

The advisory strongly recommends that vessels coordinate voyage pl  anning with U.S. Naval Forces Central Command (NAVCENT) and its Naval Cooperation and Guidance for Shipping (NCAGS) unit, which maintains a 24/7 watch on regional maritime security threats.

In a notable shift from some previous guidance, vessels are recommended to keep their Automatic Identification System (AIS) transponders on unless specifically advised otherwise by NAVCENT. The advisory notes that "some vessel seizures by Iranian forces were claimed to be a result of vessels not transmitting on AIS."