What Is the Strait of Hormuz and Why Does Trump Want to Blockade It?

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Updated: Apr 13, 2026 5:38 PM CUT

Published: Mar 18, 2026 1:06 PM CUT

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Updated: Apr 13, 2026 5:38 PM CUT

Published: Mar 18, 2026 1:06 PM CUT

The struggle over a crucial passage between the Persian Gulf and the Gulf of Oman through which around a fifth of global oil production flows is straining the already fragile U.S.-Iran cease-fire.

President Donald Trump launched a U.S. naval blockade of Iran's ports in the Strait of Hormuz Monday morning, vowing to interrupt any ship “trying to enter or leave.”

The move came after a marathon 21-hour negotiation between U.S. and Iranian officials in Islamabad over the weekend failed to yield a deal, and after weeks of Trump demanding that Iran stop its restrictions on the vital waterway.

Soon after the blockade came into effect, Trump warned Iran not to retaliate with “fast attack” ships. 

“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 vowed, seemingly referencing U.S. strikes in the Caribbean Sea and Eastern Pacific Ocean which largely targeted Venezuelan vessels.

Trump went on to champion the naval operation, telling White House reporters that Iranians are currently doing no business in the Strait and the U.S. is “going to keep it that way, very easily.”

Iran has already responded to Trump’s blockade with a warning of its own, vowing to retaliate against Gulf ports.

An Iranian military spokesperson said any U.S. restriction on vessels in international waters would be illegal and amount to "piracy.” If Iranian ports are threatened, no port in the Gulf or Gulf of Oman will remain safe, the spokesperson said, according to state media.

Amid the back-and-forth threats, oil prices surged once more to around $102 per barrel Monday morning.

Here’s what to know about the Strait of Hormuz, Trump’s attempt to blockade it, and the continued impact on the global economy as the passage remains disrupted.

What is the Strait of Hormuz?

With Iran to the north, and Oman and the United Arab Emirates (UAE) to the south, the Strait is just 30 miles wide at its narrowest point. 

Top oil and liquified natural gas (LNG) producers, including Saudi Arabia, Kuwait, Iraq, Qatar, and the UAE, export the majority of their cargo through the Strait on tanker vessels.

“It's a critical node in the global economy for all sorts of commodities, energy and otherwise,” Jim Krane, a fellow for energy studies at Rice University’s Baker Institute for Public Policy, tells TIME.

He adds that the Strait also transits around 45% of global sulfur exports, which is needed in the production of fertilizer, and the refining of metals including copper, cobalt, and nickel. 

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What is a blockade?

Per the U.S. navy commander’s handbook on naval operations law, a blockade is defined as an “operation to prevent vessels and/or aircraft of all States, enemy and neutral, from entering or exiting specified ports, airfields, or coastal areas belonging to, occupied by, or under the control of an enemy state.”

Only the President or Secretary of Defense (in this case, Pete Hegseth) can direct establishment of a blockade by U.S. forces and it “must not bar access to or departure from neutral ports and coasts.”

The President and Central Command outlined in statements ahead of the blockade that all vessels in and out of Iranian ports will be targeted, but vessels from or heading to other ports in the region will not.

How is Trump planning to blockade the Strait?

The U.S. blockade on any ships entering or leaving Iranian ports in the Strait came into effect at 10 a.m. ET on Monday.

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The U.S. Central Command has said “the blockade will be enforced impartially 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.”

But what exactly the blockade will look like as the first critical days unfold remains somewhat unclear.

“What I'm seeing is most likely an attempt to replicate the pressure campaign on Venezuela against Iran right now,” Noam Raydan, a senior fellow at The Washington Institute for Near East Policy, tells TIME. “Iran has military capabilities, and most likely it will retaliate. This is the difference between Iran and Venezuela.”

Krane refers to the mission as a gamble—one that “ratchets up” the pressure on Iran and could ultimately escalate or de-escalate the current situation.

“That's the Trump Administration's logic, to crank up the pressure in a way that doesn't get anybody killed and keeps the cease-fire intact,” he argues.

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“The U.S. had a card in their pocket to play if the [negotiation] talks failed. They’re playing that card,” adds Krane, noting that the potential impact on Iran’s finances could force a return to negotiations.

The U.S. blockade follows mounting reports that Tehran may be charging certain vessels tolls for safe passage through the waterway.

Addressing tolls in the Strait and beyond, Trump said he has instructed the U.S. Navy to “seek and interdict every vessel in international waters that has paid a toll to Iran,” insisting that “no one who pays an illegal toll will have safe passage on the high seas.”

He also vowed to clear any sea mines Iran may have laid. 

U.S. Central Command (CENTCOM) previously confirmed forces had set the conditions for clearing mines in the Strait, with two U.S. Navy guided-missile destroyers conducting operations.

“De-mining is really laborious, painstaking work. It’s much easier to lay some mines than it is to get rid of them,” says Krane.

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How have the markets reacted to Trump’s blockade?

Following Trump’s blockade announcement, prices surged on Monday as markets opened, with Brent crude oil prices reaching $102 per barrel, up from $94 when markets closed Friday. 

On Monday, the national average price for gas reached $4.12 per gallon, up from an average of $3.12 per gallon in the week prior to the initial U.S.-Israeli strikes against Iran.

“Enjoy the current pump figures. With the so-called 'blockade,’ soon you'll be nostalgic for $4–$5 gas,” said Iran’s parliament speaker Mohammed Ghalibaf in response to the market instability.

But, unlike before, the U.S. blockade will likely see Iranian oil removed from the market, which so far has been able to pass through the Strait during the conflict.

The blockade “essentially takes off another almost 2 million barrels a day of oil and refined products off the world market,” estimates Krane, noting the added stretch on the global economy.

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“From an oil market perspective, this is just adding to the pressure on oil markets. It's taking more supply offline at a time when there's already a shortage,” he says.

How have other countries responded to Trump’s Strait of Hormuz blockade?

Trump’s relationship with several European leaders has become strained during the Iran war, especially after he threatened to pull the U.S. out of NATO after allies refused his previous request to send warships to the Strait.

Now, the U.S. blockade has stirred further tension.

British Prime Minister Starmer, whose once strong relationship with Trump appears to have diminished, was clear that the U.K. will not be involved in the U.S. efforts.

“It is, in my view, vital that ​we get the Strait open and fully open, and that's where we've put ​all of our efforts in the last few weeks and we'll ⁠continue to do so,” he said, emphasizing the U.K. is “not supporting” the blockade.

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French President Emmanuel Macron said that France, alongside the U.K., “will organize a conference with those countries prepared to contribute alongside us to a peaceful multinational mission aimed at restoring freedom of navigation in the Strait” in the coming days. 

“This strictly defensive mission, separate from the warring parties to the conflict, is intended to be deployed as soon as circumstances permit,” he added.

In line with her government’s vocal opposition to the U.S.-Iran war, Spanish Defense Minister Margarita Robles was especially critical of the blockade, arguing that it “makes no sense.”

“This is another episode in the downward spiral the world has been dragged into,” she said.

A smoke plume rises following a drone strike sparking a fuel tank fire nearby Dubai International Airport in the United Arab Emirates on March 16, 2026. AFP—Getty Images

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How has Iran disrupted the Strait of Hormuz since the start of the war?

Following the initial U.S.-Israeli strikes against Iran on Feb. 28, Iranian officials have used the Strait of Hormuz as a geopolitical bargaining chip.

In March, Iran’s new Supreme Leader Mojtaba Khamenei, in his first statement since succeeding his father, vowed to keep holding the key waterway as “leverage.”

At least 17 tankers have been targeted in the region, bringing transit to a virtual standstill, with vessels no longer willing to risk the treacherous trade route.

One of the most recent incidents came on April 7, when a vessel 25 nautical miles off the Iranian coast “was struck by an unknown projectile,” causing damage above a waterline on the ship, per a report issued by the United Kingdom Maritime Trade Operations center. 

According to the International Energy Agency (IEA) oil report, Gulf producers exported 3.3 million barrels per day (mb/d) of refined products and 1.5 mb/d of LPG in 2025. At present, more than 3 mb/d of refining capacity in the region has already shut due to attacks and a lack of viable export outlets.

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And it's not only upstream production and exports that have been disrupted, as numerous oil refineries and facilities have closed due to strikes or fear of potential attacks.

When the U.S. and Iran entered a two-week cease-fire on April 7, Trump did so on the condition of a "complete, immediate, and safe opening" of the Strait of Hormuz. But that failed to happen.
Iran's continued chokehold on the transit of oil and gas has upended the global economy, causing major instability to energy prices around the world.

“The key point when it comes to the Strait of Hormuz is that there is really no other exit point for the magnitude of energy flow,” Joel Hancock, an energy analyst at investment firm Natixis CIB, tells TIME. “The Strait of Hormuz is a true chokepoint in the sense that you are seeing production being shut in, because there isn't really an alternative exit route.” 

In short, even if journeys can be adjusted, alternative routes simply can’t handle the same volume of oil.

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Who typically controls the Strait of Hormuz?

The Strait of Hormuz does not officially fall under Iran’s control. 

All vessels that wish to journey the waterway should be able to do so. But Iran has a unique capability, due to its physical proximity, to exert significant influence over the passage and effectively shut it down, as it has done these past few weeks.

As part of cease-fire negotiations, one of Iran’s proposal points was to allow for Tehran’s full control over the Strait of Hormuz—a request the U.S. and others, particularly in the Gulf region, would likely reject.

Iran’s military build-up in the region has allowed the regime to exert significant authority over the Strait, and what can ultimately pass through, according to Michael Eisenstadt, director of the military and security studies program at The Washington Institute for Near East Policy.

“Iran has built up, in the last several decades, a very large number of area denial systems,” Eisenstadt tells TIME, citing “anti-ship cruise missiles, mines, submarines, surface to air missiles, and drones” as examples.

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Read More: What to Know About the Bab El-Mandeb Strait as Iran Threatens to Restrict Other Key Trade Passage

Has Iran blocked the Strait of Hormuz before?

Iran has threatened to close and restrict the Strait on numerous occasions.

During the Iran-Iraq conflict in the 1980s, the “Tanker War” saw both Iran and Iraq launch hundreds of attacks against oil tankers and vessels in the Persian Gulf and Strait of Hormuz. 

The attacks in the Tanker War were much worse, experts note, in terms of the number of vessels struck and destroyed.

“You had hundreds of ships that were hit,” says Krane. “But the impact on the global economy was not nearly as dire. Current attacks are having a much larger impact on oil markets in the global economy with much less hostile action by Iran.”

Attacks in the 1980s notably did not bring passage through the Strait to a halt, adds Eisenstadt, highlighting the “intermittent” nature of the strikes back then.

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Years later, in 2011, Iran’s then-Vice President Mohammad Reza Rahimi declared that oil would not pass through the waters if Western sanctions against Iran were widened. The sanctions were issued as a result of concerns over Iran’s nuclear capabilities.

The same issue ignited during last year’s conflict, dubbed the “12-day war,” which ultimately saw the U.S. join Israel in launching strikes on three key Iranian nuclear facilities.

During that conflict, Iran’s parliament voted to close the Strait—a largely symbolic gesture, given that it doesn’t have official authority over the passage.

The move, however, did cause jitters in the markets, with the price of crude oil futures jumping to $80 per barrel in the immediate aftermath of the vote—somewhat serving as a warning sign for the economic and trade turmoil that was yet to come.