What Is the U.S. Blockade of Iran? How It Works and When It Began

It stops Iran’s sea trade in both directions. Central Command said from the first day that the naval blockade covers every vessel entering or leaving Iranian ports and coastal areas, on the Gulf and on the Gulf of Oman, and that it applies to ships of all nations, not only Iranian-flagged ones.

Oil is the main target. Most of Iran’s crude is loaded at the Kharg Island terminal in the northern Gulf, and most of its container trade runs through Bandar Abbas, on the strait. Interceptions have taken place mainly in the Gulf of Oman and the northern Arabian Sea, where U.S. warships meet ships before they reach Iranian waters. Humanitarian cargo cleared by U.S. forces is the one stated exception.

No. The U.S. blockade and the closure of the Strait of Hormuz are separate measures imposed by opposite sides. Central Command said in April that it would not stop ships sailing through the strait to and from non-Iranian ports, and Defense Secretary Pete Hegseth and Gen. Dan Caine, chairman of the Joint Chiefs, described it on April 16 as a blockade of Iran’s ports and coastline, not of the waterway.

The restrictions on the strait itself come from Iran, which uses them as leverage against the blockade. Tehran reclosed the strait on April 18, citing the U.S. refusal to lift the blockade, and closed it again after the blockade returned in July. Daily traffic is tracked on our Strait of Hormuz status page.

President Donald Trump announced the blockade on April 12, 2026, hours after the first round of U.S.-Iran talks in Islamabad ended without a deal. Central Command began enforcing it at 10 a.m. Eastern time on April 13 under a presidential proclamation.

The first phase ended on June 18. Trump and Iranian President Masoud Pezeshkian had signed a memorandum of understanding on June 17 that required the United States to end the blockade within 30 days, and Central Command said the next day that U.S. forces had “lifted the blockade on all maritime traffic entering and exiting Iranian ports and coastal areas.”

The pause lasted less than a month. After a series of Iranian attacks on ships in the strait, Trump announced on July 13 that the blockade would return. It took effect at 4 p.m. Eastern time on July 14, alongside U.S. strikes on Iranian coastal targets, and Iran’s deputy foreign minister, Kazem Gharibabadi, declared the memorandum no longer valid.

U.S. forces stop ships at sea and use force when they refuse. Central Command said on April 16 that more than 10,000 personnel, more than 12 warships and more than 100 aircraft were committed to the operation.

A ship heading for Iran first gets a radio warning and an order to turn around. If it refuses, it can be boarded; if it keeps going, it can be disabled. The first ship fired on was the Iranian-flagged container ship Touska. On April 19, after about six hours of warnings, the destroyer USS Spruance fired several 5-inch rounds into its engine room, and Marines flown from the amphibious assault ship USS Tripoli boarded and seized it.

Central Command said on October 5 that since the blockade resumed its forces had redirected 130 commercial vessels and disabled three that refused to comply. On October 31 it put the number of redirected ships at 144. “We will swiftly act against any vessels trying to run the blockade,” Adm. Brad Cooper, the head of Central Command, said in October.

By the U.S. measure, it has cut Iran’s seaborne trade almost to nothing. Cooper said on October 16 that the blockade had kept at least $25 billion of Iranian crude off the market. “With the exception of the humanitarian assistance we’ve allowed in, Iran has no exports and no imports by sea,” he said.

Tehran’s answer is that it has absorbed the blow. Pezeshkian wrote on October 4 that pressure on the economy had grown but that the enemy’s goals in the economic war had not been met, as covered in our report on Hegseth’s “ironclad” remark. The blockade has not yet produced the outcome Washington wants, which is a deal on its terms.

Under the law of naval warfare, a blockade is a measure only a party to an armed conflict may use. The rules, set out in the San Remo Manual of 1994, require that a blockade be declared and notified, that it actually be enforced, that it apply to ships of every nation alike, and that it let essential supplies for civilians through under conditions.

Washington has run this one along those lines, with a formal start time, an all-flags rule and a humanitarian exception. Tehran rejects it outright. Araghchi called the blockade of Iranian ports “an act of war” on April 21, and Iran called the seizure of the Touska armed piracy. In 1962 President John F. Kennedy called his naval cordon around Cuba a “quarantine” because a blockade is an act of war.

Lifting it is the first step Iran demands. Iranian state media listed an end to the naval blockade, the release of frozen assets and an end to the war on all fronts as Tehran’s conditions on September 22. On November 1, Araghchi said the latest plan cut implementation to two days: Washington acts on day one, and “on day two, the Hormuz Strait will reopen.”

Washington’s position is to keep the pressure on until Iran gives way. Hegseth called the blockade “ironclad” on October 3, and Secretary of State Marco Rubio said on October 31 that Trump had not decided whether to resume strikes. Neither side has yet offered a step the other can accept.