After US-Iran peace talks in Pakistan collapsed at the weekend, US President Donald Trump said the US Navy would block ships entering or leaving any Iranian port or coastal facility via the Strait of Hormuz.
Until the war began in late February, about a fifth of the world’s seaborne oil trade passed through Hormuz, the narrow waterway between the Persian Gulf and the Indian Ocean. If enforced, the blockade would cut off Iran’s main revenue source by halting nearly 2 million barrels per day of oil exports, a move Trump hopes will force Tehran back to negotiations.
US officials said the aim was to strip Iran of leverage gained from controlling the waterway, which Tehran effectively closed when the war began and stranded hundreds of oil and gas tankers. Trump also framed the blockade as stopping Tehran from charging vessels up to $2 million for safe passage. He warned on Truth Social that any ship paying an “illegal toll” would not have safe passage and said the US Navy would begin destroying mines Iran laid in the strait.
The United States Central Command (CENTCOM) said the blockade would not affect vessels traveling to and from non-Iranian ports such as Saudi Arabia, Qatar and the United Arab Emirates. CENTCOM announced the operation with a notice to mariners, saying it would be enforced in the Gulf of Oman and Arabian Sea east of the Strait of Hormuz and would include the entirety of the Iranian coastline, not limited to ports and oil terminals. The advisory said any vessel entering or departing the blockaded area without authorization is subject to interception, diversion and capture.
Maritime law experts said enforcement would rely on the naval right of visit and search, where US warships stop and inspect tankers and can divert them if suspected of carrying Iranian oil. While visit and search has precedent in naval warfare, several experts warned the blockade risks crossing into disputed areas under maritime law, affecting neutral ships and causing long-term disruption of a critical international waterway.
Within hours of the blockade starting, shipping data showed tanker traffic through the strait had mostly halted. CENTCOM later said no ships had made it past the blockade and six vessels complied with orders to return to port. Trump warned Iran against retaliation, saying the country’s remaining “fast attack ships” would be “eliminated” if they approached the blockade.
A US blockade could sharply curtail Iran’s ability to load and ship crude from its main export terminal, Kharg Island, which handles more than 90% of the country’s oil shipments. Iran has continued exporting despite sanctions by using a shadow fleet of aging tankers and ship-to-ship transfers off Malaysia and other evasion tactics. The US had also previously granted Iran temporary permission to sell oil to help stabilize markets during the conflict. The new naval blockade makes such loadings far riskier, as operators face boarding, diversion or seizure.
In 2025, Iran’s oil exports totaled around $45 billion, or about 13% of GDP, according to Capital Economics. With no land pipelines to reroute crude, Iran has few non-sea export options; even its Jask terminal on the Gulf of Oman could be subject to US search. Sustained US pressure could force Tehran back to talks as it loses revenue.
The blockade prompted threats of retaliation from Iran’s Revolutionary Guard Corps, which warned that restrictions on Iranian ports would make no port in the Gulf and Sea of Oman safe, raising fears of strikes on energy or shipping infrastructure in Gulf states. Ebrahim Rezaei, a spokesperson for the Iranian parliament’s National Security Commission, said Tehran was prepared to respond militarily if necessary and suggested Iran might reveal other measures it has not yet used.
Several US experts questioned the move, warning it could draw the US into an open-ended military commitment. Dana Stroul, a former senior Pentagon official, said the mission is difficult to execute alone and likely unsustainable over the medium to long term. Neil Shearing of Capital Economics suggested the blockade may also be intended to pressure Beijing into mediating a ceasefire and reopening trade through the strait; China, which has bought 80–90% of Iran’s seaborne crude in recent years, stands to lose the most economically. Shearing also raised the prospect that seizing allied ships that paid tolls to Tehran or Chinese vessels would represent a significant escalation.
China’s Foreign Ministry denounced the blockade as “dangerous and irresponsible,” while President Xi Jinping said Beijing was willing to play a constructive role in promoting peace in the Middle East.
Edited by: Tim Rooks
