CENTCOM launches naval blockade of all Iranian ports

U.S. Central Command announced Sunday that American forces would begin enforcing a full naval blockade of all Iranian ports effective April 13 at 10 a.m. ET, acting under a presidential proclamation issued by President Donald Trump.

The operation is narrowly focused on Iranian ports and coastal areas, while allowing international shipping to continue transiting the Strait of Hormuz so long as vessels are not bound for Iran. The order came hours after diplomatic talks in Islamabad ended without agreement, collapsing a fragile ceasefire framework that had been in place for roughly two weeks.

CENTCOM stated that “the blockade will be enforced impartially against vessels of all nations entering or departing Iranian ports and coastal areas, including all Iranian ports on the Arabian Gulf and Gulf of Oman.” The command was unambiguous on one critical point: U.S. forces “will not impede freedom of navigation for vessels transiting the Strait of Hormuz to and from non-Iranian ports,” an apparent scaling back from President Trump’s earlier threat to blockade the entire strait.

To manage commercial traffic during the transition, CENTCOM advised mariners to monitor Notice to Mariners broadcasts and maintain radio contact with U.S. naval forces via bridge-to-bridge channel 16 when operating in the Gulf of Oman and Strait of Hormuz approaches. Additional formal guidance to commercial mariners was expected to be issued prior to the blockade’s start time.

Iran wasted no time responding. The Islamic Revolution Guards Corps declared in a statement Sunday that any attempt by military vessels to transit the Strait of Hormuz would be deemed a violation of the two-week ceasefire with the United States, warning it would respond with a “firm and decisive” reaction. The IRGC claimed that the strait remained under its “intelligent control and management,” and stated that civilian vessels could transit the waterway only under what it described as “specific regulations.” The Guards also warned that enemies would be trapped in a “deadly vortex” in the event of any miscalculation.

The blockade order followed the breakdown of the first direct U.S.-Iran negotiations in over a decade. Talks in Islamabad, where a U.S. delegation met face-to-face with Iranian counterparts, concluded without agreement. Vice President JD Vance, who led the American delegation, said Iran “chose not to accept our terms,” with Washington’s core demand being that Tehran abandon its nuclear program. Iran, for its part, pushed back on terms it said failed to address its fundamental concerns, including war reparations, comprehensive sanctions relief, and a broader regional ceasefire that would extend to Lebanon.

Until the U.S.-Israeli war against Iran began on February 28, roughly 25% of the world’s seaborne oil trade and 20% of global LNG passed through the strait. Since then, the IRGC has largely blocked the waterway, launching 21 confirmed attacks on merchant ships and reportedly laying sea mines in the strait. Tehran also floated the idea of a toll system under which tankers would pay Iran for passage — a proposal Washington characterized as extortion.

The two-week ceasefire — which was supposed to hold until April 22 — now appears in serious jeopardy. The fragile pause in hostilities had been paving the way for the evacuation of approximately 20,000 sailors aboard roughly 2,000 ships stranded in the Persian Gulf amid the conflict. With the blockade now in effect and Iran’s IRGC threatening to treat any approaching warship as a ceasefire violation, the situation in the Gulf has moved rapidly toward a new and more dangerous threshold.

Whether CENTCOM’s naval forces can enforce the blockade without triggering a direct military engagement with IRGC naval and air assets remains the central operational question. Iranian small-boat tactics, sea mines, and shore-based anti-ship missile batteries present real risks to any enforcement mission in the confined waters of the Arabian Gulf. The Department of War has not publicly disclosed which specific naval assets are assigned to the blockade operation, but recent weeks have seen American guided-missile destroyers operating in the region, including transits through the Strait of Hormuz itself that Iranian forces attempted to turn back.

The collapse of the Islamabad talks leaves the broader diplomatic track in disarray. Both sides entered the negotiations with deep mistrust and emerged with none of their core demands met. With a ceasefire fraying and a naval blockade now underway, the window for a negotiated off-ramp is narrowing considerably.