How will Trump’s blockade of Iranian oil work?
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 primary source of revenue by halting its roughly 2 million barrel-per-day oil exports, a move Trump hopes will force Tehran back to the negotiating table.
US officials said the objective is to remove the leverage Iran gains from control of the waterway, which Tehran effectively shut when the war began, stranding hundreds of oil and gas tankers. Trump also framed the blockade as stopping Tehran from charging vessels up to $2 million for safe passage. “No one who pays an illegal toll will have safe passage on the high seas,” he wrote on Truth Social, adding that the US Navy would “begin destroying the mines the Iranians laid” in the strait.
The United States Central Command (CENTCOM) said the blockade would not affect vessels traveling to and from non-Iranian ports, including Saudi Arabia, Qatar and the United Arab Emirates.
How will the US Navy enforce the blockade?
The operation, announced with a notice to mariners and which began on Monday, will be enforced in the Gulf of Oman and Arabian Sea east of the Strait of Hormuz and, CENTCOM said, would include the entirety of the Iranian coastline, not limited to ports and oil terminals. The advisory warned that 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 right of visit and search, allowing US warships to stop and inspect tankers and divert them if suspected of carrying Iranian oil. While visit-and-search has precedent in naval warfare, several experts cautioned the blockade risks entering disputed legal territory, affecting neutral ships and disrupting a crucial international waterway over the long term.
Within hours of the blockade’s start, shipping data showed tanker traffic through the strait had mostly stopped; at least two tankers were turned back after attempting to cross. Trump warned Iran against retaliation, saying the country’s remaining “fast attack ships” would be “eliminated” if they approached the blockade.
How quickly could the blockade hit Iran’s oil exports?
A US blockade could sharply limit 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 to export despite sanctions by using a shadow fleet of aging tankers, ship-to-ship transfers off places like Malaysia and other evasion tactics. The US had also at times given Iran temporary permission to sell oil to help stabilize markets during the conflict; the blockade would make such loadings far riskier as operators face the threat of boarding, diversion or seizure.
In 2025, Iran’s oil exports were about $45 billion, or roughly 13% of GDP, according to Capital Economics. With no land pipelines to reroute crude, Tehran has few non-seaborne export options; even its Jask terminal on the Gulf of Oman could be subject to US Navy searches. Sustained US pressure could therefore deplete revenues quickly and push Iran back to negotiations.
Could the blockade lead to a wider conflict?
Iran’s Revolutionary Guard Corps responded to the blockade threat with retaliation warnings, saying that if Iranian ports faced restrictions “no port in the Gulf and the Sea of Oman will be safe,” stoking fears of attacks on energy or shipping infrastructure in neighboring Gulf states. Ebrahim Rezaei, a spokesman for the Iranian parliament’s National Security Commission, warned Tehran was prepared to respond militarily if necessary, writing on X that the blockade would complicate the situation for Trump and could prompt Iran to reveal other “cards” it has not yet used.
Several US experts questioned the move, suggesting it risks drawing the United States into an open-ended military commitment. “Trump wants a quick fix. The reality is, this mission is difficult to execute alone and likely unsustainable over the medium to long term,” said Dana Stroul, a former senior Pentagon official.
Neil Shearing, chief economist at Capital Economics, suggested the blockade might also be intended to pressure Beijing into mediating a ceasefire and reopening trade through the strait; China has bought some 80–90% of Iran’s seaborne crude in recent years and would stand to lose significantly. Shearing also wondered whether the US would seize allied ships that paid Tehran’s tolls or Chinese vessels in the strait, an action that would represent a major escalation.
Edited by: Tim Rooks