Sweeping for underwater explosives could take months despite a tenuous ceasefire between the United States and Iran in the weekslong war, experts say. Any future claims that the U.S. cleared the waterway where 20% of the world’s oil typically passes might fail to convince commercial freighters and their insurers that it is finally safe.

“You don’t even have to have lain mines — you just have to make people believe that you’ve laid mines,” said Emma Salisbury, a scholar at the Foreign Policy Research Institute’s National Security Program.

“And even if the U.S. sweeps the strait and says everything’s clear, all the Iranians have to do is say, ‘Well, actually, you haven’t found them all yet,’” said Salisbury, who is also a fellow at the Royal Navy Strategic Studies Centre. “There’s only so much the U.S. can do to give that confidence back to commercial shipping.”

Seeking out mines is one of the latest tactics announced by the Trump administration to get traffic moving again through the strait as rising energy prices and wider economic effects pose a political risk. The U.S. also has blockaded Iran’s ports, seized ships tied to Tehran and planned to take part in a second round of ceasefire talks in Pakistan this weekend.

Hegseth doesn’t deny that mine-clearing could take 6 months

Pentagon officials told lawmakers it would likely take six months to clear the mines that Iran has set in the strait, according a person familiar with the situation who spoke on condition of anonymity to discuss the sensitive information. The information was delivered during a classified briefing at the House Armed Services Committee on Tuesday.

When asked about the estimate, Defense Secretary Pete Hegseth told reporters Friday that the military would not speculate on a timeline, but he did not deny it.

“Allegedly that was something that was said,” Hegseth said at a Pentagon news conference. “But we feel confident in our ability, in the correct period of time, to clear any mines that we identify.”

Trump said he has ordered the Navy to attack any boat laying mines in the strait.

“Additionally, our mine ‘sweepers’ are clearing the Strait right now,” the president said on social media Thursday. “I am hereby ordering that activity to continue, but at a tripled up level!”

Adm. Brad Cooper, the top U.S. commander in the Middle East, recently told reporters that the military would be working to clear mines from the strait. He did not offer details.

There is no indication that the U.S. military is using warships, its most visible mine-clearing assets, in the strait now.

But the Navy also has divers and small teams of explosive ordnance disposal technicians in the region that are capable of clearing mines. They are a less obvious target than a large warship.

Experts also say some mine-clearing equipment could be moved off ships and deployed from land.

It’s easier for Iran to lay mines than it is to find them, expert says

It is unclear whether a single mine has been deployed. Iran has mentioned only the “likelihood” of mines in the strait’s prewar routes.

Estimates of Iran’s mine stockpiles are in the low thousands, said Salisbury, of the Foreign Policy Research Institute. Most of its underwater explosives are believed to be older Soviet models. Some of its newer ones may be from China or made domestically.

“Minelaying is a lot easier than minesweeping, so you can literally push these things off the back of a speedboat,” Salisbury said, though she noted the U.S. could likely see that.

Iran also has small submarines that can lay mines and are much harder to detect, Salisbury added. She said she has not seen indications that they have been destroyed in the war.

If Iran has set mines in the strait, they are not the spiky balls floating on the surface seen in the movies, Salisbury said. The explosives are likely sitting on the seabed or moored to it by a cable and floating under the surface. They can be triggered by the water pressure changing when a ship passes or by the sound of its engine.

How the US can sweep for mines in the strait

The U.S. Navy now has two littoral combat ships in the Middle East that are capable of sweeping for mines, said a defense official, who spoke on condition of anonymity to discuss sensitive military movements.

Two U.S. Avenger-class minesweepers based in Japan also have departed for the Middle East but were in the Pacific Ocean as of Friday, the official said.

Steven Wills, a retired lieutenant commander who served on an Avenger-class ship, said the Navy is likely looking for sea explosives in order to create a safe channel through the strait. Minesweeping is a slower process that usually occurs after a conflict.

“Minehunting is walking through your yard pulling individual weeds and dandelions so that you can walk safely from one side to the other. Minesweeping is more like mowing the grass,” said Wills, an expert at the Center for Maritime Strategy at the Navy League of the United States.

Scott Savitz, a researcher with the RAND Corp. who focuses on naval operations and mine clearing, said the Navy does not necessarily have to remove every last mine.

“There’s still areas that have not been cleared from World War II — and in some cases, World War I — just because it is so resource intensive and it takes a lot of time,” he said.

Teams on the Navy’s littoral combat ships can deploy remotely operated, uncrewed vehicles that use sonar and other technology to find mines, Wills said. They also carry charges to destroy the explosives.

U.S. Navy ships may also have explosive ordnance disposal teams, including divers, that can hunt for and destroy mines, Wills said. Helicopters can search for mines using lasers.

Shipping companies are weighing the risks

Eventually, shipping companies will be willing to take some risks to travel through the strait “particularly given how lucrative it is,” Savitz said.

Under Iran’s approval procedure for vessels wanting to transit the strait, ships must take a different route than before the war — to the north, near Iran’s coastline.

Insurers are adding a clause that requires ship owners to contact Iranian authorities to ensure safe passage, said Dylan Mortimer, U.K. marine war leader for insurance broker Marsh.

That certification does not mention mines specifically and is intended to protect against the entire spectrum of threats, including missile and drone attacks or seizures, Mortimer said.

But mines do, at the very least, play a psychological role, a phenomenon Mortimer called the “specter of threat.”

“That plays in the Iranians’ favor, because whether there are mines there or not, people think there’s mines there and they will operate accordingly,” Mortimer said.

Those fears could mean it takes longer to restore confidence that the strait is safe even after the war.