The U.S. government warned American-flagged commercial vessels to exercise extreme caution while transiting the Strait of Hormuz and surrounding waters.
The warning cited a continuing pattern of illegal Iranian boardings and seizures that threaten global commerce and U.S. national security.
In a new maritime advisory released by the Department of Transportation, officials said commercial vessels in the Persian Gulf, Strait of Hormuz, and Gulf of Oman "have long been at risk of being hailed, queried, boarded, detained, or seized by Iranian forces."
The advisory noted that Iranian forces have historically used small boats and helicopters during boarding operations and have attempted to force vessels into Iranian territorial waters — including as recently as Feb. 3, 2026, according to the release.
The warning comes as tensions remain high in the region, and Iran continues to test U.S. resolve and international law.
Conservatives have long argued that Tehran only escalates when it senses weakness, and the new advisory underscores how critical maritime security has become for America's economy and energy supply chains.
The department said the U.S. government is "continually assessing the maritime security situation" to safeguard freedom of navigation and ensure the free flow of commerce.
Under the guidance, U.S.-flagged vessels hailed by Iranian forces are instructed to provide their vessel name and flag state and affirm they are proceeding in accordance with international law as reflected in the Law of the Sea Convention.
If Iranian forces attempt to board, ship masters are advised — if safety permits — to decline permission and again state the vessel is operating lawfully.
However, the advisory stressed that crews should not forcibly resist if boarded.
"Refraining from forcible resistance does not imply consent or agreement to that boarding," the release stated.
The DOT also recommended that vessels stay as far as possible from Iran's territorial sea and that eastbound vessels in the Strait of Hormuz transit close to Oman's territorial waters.
The advisory urged ships to coordinate voyage planning with U.S. Naval Forces Central Command's Naval Cooperation and Guidance for Shipping, which maintains a 24/7 watch and provides real-time threat information.
Vessels are also advised to keep Automatic Identification System transponders active unless directed otherwise, noting that some Iranian seizures have been blamed on vessels not transmitting AIS.
In addition, U.S.-flagged vessels are urged to register with the United Kingdom Maritime Trade Office prior to entering the Indian Ocean Voluntary Reporting Area and to monitor VHF Channel 16.
The warning highlights a broader reality: Iran continues to behave like a rogue regime, threatening lawful international shipping and using intimidation tactics to disrupt commerce.
The advisory supersedes a previous U.S. Maritime Advisory and will remain in effect until Aug. 8, 2026.
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