WASHINGTON — The Strait of Hormuz, the world’s most critical oil transit chokepoint, is increasingly turning into a blind spot for global shipping.

Commercial traffic through the narrow waterway has dropped sharply since the US resumed strikes on Iran two weeks ago, with vessel movements falling to levels not seen since the peak of the conflict. As insurance premiums surge and security concerns intensify, some ships are still attempting the passage — but not always in plain sight.

Iran has said the waterway is closed and has warned that ships attempting to pass through the international strait without Tehran’s explicit approval could be targeted. Washington maintains that the Strait of Hormuz remains open, though not for vessels traveling to or from Iranian ports.

Maritime analysts say some vessels are vanishing from public tracking platforms, while others appear to be steering closer to the Iranian side of the tight corridor. The shifting routes are fueling new concerns over whether Tehran is exerting more control over a vital artery of global commerce — and whether it may be collecting revenue from ships seeking safer passage.

The irregular shipping patterns follow weeks of Iranian attacks and threats aimed at commercial vessels, a campaign that has dramatically reduced the number of ships willing to cross the strait.

Only about 15 ships were tracked moving through the Strait of Hormuz between Thursday and Friday, roughly half the average traffic seen during the US-Iran cease-fire. Before the war, daily traffic through the chokepoint typically ranged from 130 to 150 vessels.

Public tracking sites, however, may no longer be showing the full extent of activity. Maritime intelligence firms say some captains are switching off their Automatic Identification System, or AIS, transponders before entering the high-risk zone.

The result is growing uncertainty over how much trade is still moving through Hormuz — and whether Iran is finding ways to profit from that traffic despite sweeping US sanctions.

Earlier reporting during the conflict suggested some commercial shippers were asked to pay as much as $2 million for assurances of safe passage through waters threatened by Iran and its Islamic Revolutionary Guard Corps.

However, there has been no public accounting of how many vessels ultimately agreed to such arrangements or whether the practice continues.

If ships are paying such fees, even on a limited basis, the regime could be generating tens to hundreds of millions of dollars while maintaining pressure on one of the world’s busiest maritime corridors.

The true figure, however, remains impossible to verify publicly because so much shipping activity is now obscured from open-source tracking.

But any amount is too much, according to US officials.

Secretary of State Marco Rubio warned this week that allowing Tehran to dictate access through the strait would create a “dangerous precedent,” arguing that freedom of navigation remains a vital US national security interest.

“If we create a precedent in the Middle East where a nation-state can decide that they are going to control an international waterway, charge a toll, and if you don’t pay them, blow up your ships, we have created a very dangerous precedent which will repeat itself in other parts of the world, including in this region,” Rubio said Wednesday at the annual Association of Southeast Asian Nations summit in Manila.

Asia is home to many critical waterways — such as the Strait of Malacca and the Taiwan Strait — that currently operate toll-free.

Even if Tehran isn’t collecting a dime from passing ships, it has already achieved something strategically valuable: convincing parts of the global shipping industry that navigating Hormuz now means accounting for Iran’s wishes, experts say.

“Iran’s chokehold remains, even if Washington says the waters are open,” said a regional source familiar with shipping activity in the strait.

The apparent shift has also prompted a broader question: Why isn’t the US Navy — which has as many as 20 ships in the region — stopping it?

The answer largely comes down to international law.

US warships generally cannot stop or board foreign merchant vessels simply because they are sailing near Iran or choosing a particular route through the Strait of Hormuz, Coast Guard sources and international maritime law state.

Unless a ship is violating US sanctions, transporting prohibited cargo or otherwise provides legal grounds for interdiction, merchant vessels retain the right of innocent passage through the international waterway.