US President Donald Trump’s plan for a full naval blockade of the Strait of Hormuz threatens to deepen an already unprecedented crisis in one of the world’s most important energy-producing regions.
The narrow waterway connecting the Persian Gulf to the wider world has become a flashpoint since the US and Israel began strikes on Iran six weeks ago. Tehran tightened its grip on the corridor in response, all but closing off a vital thoroughfare. A full blockade could halt the remaining flows and threaten economies far beyond the Middle East.
Transits have dwindled to single digits a day, down from about 135 in peacetime. A US naval blockade along the lines of what was carried out off Venezuela from the end of last year could reduce that to zero, pressuring Iran but also cutting off a vital source of supply for Asian nations.
It would also likely doom an already fragile ceasefire agreed last week.
What’s far less clear is how such a blockade would work in practice — or whether Washington is prepared to bear the risks of enforcing it. Here’s what we know so far.
What exactly is the US threatening to do?
Hours after peace talks in Islamabad fell apart on Sunday, Trump posted on social media that “effective immediately” the US Navy would blockade “any and all ships trying to enter, or leave, the Strait of Hormuz.” He added other countries would participate, without naming any.
He threatened to “interdict every vessel in International Waters that has paid a toll to Iran,” implying the US could impose its blockade widely, well beyond the strait and even the waters of the Gulf of Oman.
The US military separately issued a more narrow interpretation, setting a start of Monday at 10 a.m. Eastern Time for the blockade. It applies to all vessels “entering or departing Iranian ports and coastal areas,” adding that freedom of navigation through the corridor would not be impeded.
Seafarers are advised to monitor official broadcasts and contact US naval forces when in the Gulf of Oman and approaching the Strait of Hormuz, it added.
While the exact shape of the blockade is unclear, it would almost certainly involve inspecting and interdicting some vessels, possibly even boarding and seizing ships with links to Tehran, as happened with Venezuela. It is less obvious, however, that the US will want to tie up its ships pursuing tankers into the Indian Ocean, or how either side would respond to a confrontation or potential damage to a tanker.
The US has assets in the region including the USS Tripoli, an amphibious assault warship capable of rapid response. It carries 3,500 sailors and marines, in addition to stealth fighters and transport aircraft.
Iran’s Islamic Revolutionary Guard Corps responded to Trump’s call for a blockade by saying that any military vessels attempting to approach the strait “under any pretext” would be considered a violation of the ceasefire.
Why is the US doing this?
Iran’s near-total closure of Hormuz has proved an exceptionally effective asymmetric weapon, inflicting acute financial pain in a way Washington has struggled to counter, and providing a source of great frustration.
The ultimate aim of a blockade would be to cut off Iran’s oil flows, severing a vital financial lifeline for the regime.
Heading into the conflict, many experts had dismissed the possibility of a closure of the strait because Iran would not want to jeopardize its exports. Instead, Tehran has shown itself able to impede others while keeping its own shipments flowing. That has helped boost its crude revenues, while driving up global prices.
The blockade option has already been used by the Trump administration in Venezuela, squeezing an economy hit by sanctions in order to then neatly decapitate its leadership. But the Latin American producer is far smaller, relies on a far more limited fleet of vessels and is also less important to the world’s top importer of oil — China.
“This new escalation is more likely to trigger more escalations than drive conciliation. The threat alone is likely enough to dissuade legitimate international shipping from exiting the Persian Gulf,” said John Bradford, a former US naval officer and a co-founder of the Yokosuka Council on Asia-Pacific Studies.
What does this mean for Iran?
A blockade, if successfully enforced, would prove extremely painful for Iran, which relies heavily on its oil exports.
Over the past weeks, the country has benefited from higher prices and cargoes previously sold at a discount to global Brent found themselves at a premium earlier this month, thanks by a US waiver allowing purchases of previously sanctioned cargoes to boost supply. India appears to have taken two cargoes under the exemption — potentially its first since 2019.
The higher selling price for each barrel is key for Iran, which has suffered major damage from US and Israeli airstrikes and will have to make significant investments to rebuild and prop up its ravaged economy.
That windfall, worth hundreds of millions of dollars since the war began, may now be over.
What does it mean for the US?
Trump has frequently sought to pair the impact on Middle East supply with an effort to market US oil and gas output, portraying the crisis as a benefit for a top producer.
Yet US crude is not always a perfect replacement for Middle Eastern grades. And for US consumers, high benchmark prices are already driving up inflation.
Iran has shown itself well aware that it may have a greater ability to withstand pain than the US.
“Enjoy the current pump figures,” Parliament speaker Mohammad Bagher Ghalibaf, who led the Iranian delegation in Islamabad over the weekend, said in a Twitter post. “With the so-called ‘blockade’, Soon you’ll be nostalgic for $4–$5 gas.”
And what does it mean for Asian nations?
Asia has borne the brunt of the energy crisis, and further limits on Hormuz traffic would worsen the region’s plight. A US waiver on Iranian oil appears to be invalidated by the blockade — a sharp reversal — and countries that had sought bilateral agreements with Iran may now be wary of clashing with the US, further limiting their options to secure fuels and crude.
“They are so focused on Iran that they are losing sight of what they are causing to the world,” Jorge Montepeque, managing director at Onyx Capital Group, said in an interview with Bloomberg Television. “And the pain is in Asia, the pain is in the South Pacific, the pain is in anybody that depends on oil.”
