The US began its sweeping naval blockade of Iran in the Strait of Hormuz on Monday, preventing ships from leaving or entering Iranian ports through the key trade route.

The blockade — which President Trump vowed to use to end Tehran’s “extortion” of other nations transiting the critical oil chokepoint — will be enforced “impartially,” according to US Central Command.

CENTCOM noted that vessels going to or from non-Iranian ports in the Persian Gulf would not be stopped.

Fourteen ships transited the strait Sunday — while even fewer had exited or entered it each day since the US and Iran agreed to a two-week cease-fire, according to the trade data and analytics platform Kpler.

About 150 ships previously typically used the strait daily. A total of roughly 150 used it in all of last month, amid US threats and joint military action with Israel against Iran.

Neutral vessels in Iranian ports have been granted a “limited grace period” to depart the Iranian ports quickly as the blockade begins, according to the UK Maritime Trade Operations monitoring group. 

Trump announced the blockade Sunday, saying in a Truth Social post: “THIS IS WORLD EXTORTION, and Leaders of Countries, especially the United States of America, will never be extorted.”

“No one who pays an illegal toll will have safe passage on the high seas,” the president added. Iranians have sought to charge up to $2 million per oil tanker to allow passage.

Trump also issued threats against the Islamic Revolutionary Guard Corps’ fast-attack of ships in charge of patrolling the Strait of Hormuz.

More than 60% of these vessels are still intact despite the six weeks of US-Israeli airstrikes that have decimated Iran’s conventional navy.

Trump said the ships were only spared because the US “did not consider them much of a threat,” warning that the boats will be directly attacked should they interfere with America’s blockade.

“Warning: If any of these ships come anywhere close to our BLOCKADE, they will be immediately ELIMINATED, using the same system of kill that we use against the drug dealers on boats at Sea,” he wrote on Truth Social, referencing the American airstrikes on suspected narco ships in the Caribbean.

“It is quick and brutal,” he said of the airstrikes.

Despite previous suggestions that American allies would join the blockade, British Prime Minister Keir Starmer said the UK will not take part in the military venture.

“We are not supporting the blockade,” Starmer told BBC Radio on Monday, adding that London “is not getting dragged in” the US-Iran war, which entered its seventh week Saturday.

The UK will instead be joining France to host talks about reopening the Strait of Hormuz through a “strictly defensive mission,” he said.

“We will, together with the United Kingdom, organize in the coming days a conference with countries willing to contribute alongside us a peaceful multinational mission aimed at restoring freedom of navigation in the strait,” French President Emmanuel Macron said in a statement shortly before the blockade began.

Iran has condemned the US naval blockade as “piracy,” warning of retaliation across the Gulf if Tehran’s ports are shut.

“The Armed Forces of the Islamic Republic of Iran clearly and firmly declare that security of ports in the Persian Gulf and the Sea of Oman is either for everyone or for no one,” Tehran’s military said in a statement.

Iran’s parliament speaker, Mohammad Bagher Ghalibaf, went on to mock the blockade and the effects it will likely have on fuel prices.

“Enjoy the current pump figures,” he wrote on X. “With the so-called ‘blockade’, soon you’ll be nostalgic for $4–$5 gas.”

Crude oil prices jumped back above $100 per barrel after the collapse of US-Iran peace talks in Pakistan over the weekend.

US stocks also dropped immediately after markets opened, with the Dow Jones Industrial Average falling 0.7% and the S&P 500 dipping 0.3%.