By Tom Ozimek
Contributing Writer
The United States has significantly expanded the scope of its naval blockade on Iran, signaling that vessels linked to Tehran can now be boarded, searched and seized on the high seas worldwide under wartime enforcement authorities, according to Pentagon leadership and a maritime advisory circulated to commercial shipping.
The update, issued via a Joint Maritime Information Center note on Thursday citing U.S. Naval Forces Central Command, states that “all Iranian vessels, vessels with active OFAC sanctions, and vessels suspected of carrying contraband … are subject to visit, board, search and seizure,” regardless of location.
The language marks a major expansion from the original blockade announced on Monday, which targeted vessels entering or leaving Iranian ports and coastal facilities following the failure of U.S.-Iran negotiations to reach a breakthrough.
Central to the expansion is a sweeping definition of contraband that extends beyond weapons and military systems to include a wide range of dual-use goods — items with both civilian and military applications.
Broad Definition of Contraband
According to the advisory, “absolute contraband” includes weapons, ammunition, military vehicles and specialized systems. But it also designates “conditional contraband” such as petroleum, industrial materials, machinery, electronics, and communications equipment when destined for Iran and deemed supportive of its military or war-sustaining economy.
The breadth of the definition suggests the expanded enforcement could affect cargo flows beyond energy shipments, including goods traded by third countries with Iran, if U.S. officials determine they have a potential military end use.
While the blockade remains centered on Iran’s coastline and surrounding waters, the updated guidance invokes the “belligerent right to visit and search,” a doctrine in the law of naval warfare that permits interception of suspected enemy-linked shipping on the high seas.
Chairman of the Joint Chiefs of Staff Gen. Dan Caine confirmed during Thursday’s Pentagon press briefing that the blockade is being applied beyond the immediate Gulf theater, with U.S. forces prepared to pursue vessels tied to Iran across multiple operational areas.
“The joint force, through operations and activities in other areas of responsibility, like the Pacific Area of Responsibility … will pursue any Iranian-flagged vessel or any vessel attempting to provide material support to Iran,” Caine said, adding that enforcement could involve direct action at sea, including boarding and seizure.
“Turn around or prepare to be boarded if you do not comply with this blockade — we will use force,” Caine warned, describing a range of escalation options that could include warning shots and vessel takeover.
Analysts say the expanded rules, which also take aim at Iran’s so-called shadow fleet — a network of more than 500 tankers used to transport oil and other cargos under sanctions — could draw Iranian retaliation.
“Then, the ball is in Iran’s court in terms of retaliation that could include anything from boarding, ship attack, port attack and even expanding to the Red Sea,” Martin Kelly, head of advisory at EOS Risk Group, wrote in a post on X on Thursday.
Iran has previously warned that it might target all regional ports in retaliation for the U.S. blockade, and that it might seek to block all import and export traffic in the Red Sea, the Gulf of Oman and the Persian Gulf.
The Strait of Hormuz, which handles roughly one-fifth of global oil and liquefied natural gas flows, is a focal point of the crisis, with Iranian forces sharply restricting the movement of vessels in retaliation for the U.S.-Israeli military campaign.
