Trump is blockading Iranian Persian Gulf ports. What does that mean?

President Donald Trump on Monday rolled out a “blockade” of access to Iranian ports in the Persian Gulf to great fanfare, announcing his intentions on social media and then proclaiming it in motion at his appointed deadline.

But what exactly does choking access to the region’s oil exports via the Strait of Hormuz mean and what does Trump want to accomplish?

A former Biden-era Pentagon official said the U.S. is trying to turn the tables on Iran, which has blockaded the strait for weeks during the U.S.-Israeli war with the country, creating a bottleneck that roiled global markets and strained the economy. Experts say the goal of the blockade is to convince Iran’s leaders to back down and acquiesce to U.S. demands to end the war and restore freedom of navigation to the strait.

“The administration seems to be pursuing what is called a close blockade, which is an attempt to prevent ships from going into those ports or leaving those ports,” said Michael Horowitz, senior fellow for technology and innovation at the Council on Foreign Relations and a former deputy assistant secretary of Defense. “The theory behind a close blockade of Iran’s ports is to make it impossible for Iran to financially benefit from oil sales via shipping in the strait while it is restricting others from doing so.”

Iran is a top-10 petrostate, accounting for about 4% of the world’s oil production — most of which is sold to China. Shutting down the ability of Iran to export its oil could cause a significant drain on the country’s economy.

Trump announced on Sunday that he would blockade the strait, a significant escalation after a two-week ceasefire and reports that Iran was planning to toll ships seeking passage through the waterway. U.S. Central Command later clarified it would be blockading “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.”

Ports in other Middle Eastern countries, including the United Arab Emirates and Saudi Arabia, are also accessed via the strait.

Mark Cancian, a retired Marine colonel who is now a senior advisor Center for Strategic and International Studies Defense and Security Department, said the U.S. is likely to carry out the blockade in a similar fashion to the one it imposed on Venezuela last year. The U.S. seized several vessels as part of that blockade.

“We’ll know a lot more when the first boarding takes place, because that will tell us where they’re boarding ships, how they’re doing it and what happens to the ship after they board,” Cancian said.

He said the U.S. is more likely to interdict vessels east of the strait in the Arabian Sea than in the strait itself or the Persian Gulf, where Iran has more agency to interfere. Though Cancian…