Trump Says U.S. Navy Will 'Blockade' Ships in Strait of Hormuz, Raising Risk of Wider Confrontation

The phrase appeared just before dawn in Washington, in a burst of capital letters on Donald Trump’s Truth Social account: the United States Navy, he wrote, would “effective immediately … begin the process of BLOCKADING any and all Ships trying to enter, or leave, the Strait of Hormuz.”

With that Sunday post, the president signaled a potential escalation in the war with Iran at the world’s most important oil chokepoint, less than a day after U.S.–Iran cease-fire talks in Islamabad collapsed without a deal.

Trump’s online statement said he had “instructed our Navy to seek and interdict every vessel in International Waters that has paid a toll to Iran” and warned that “No one who pays an illegal toll will have safe passage on the high seas.” In another line, he declared, “Any Iranian who fires at us, or at peaceful vessels, will be BLOWN TO HELL!”

The comments, reported by news agencies that reviewed the post, went further than anything the Pentagon has publicly put on paper. They appeared to expand an already risky mine-clearance mission into what the president called a blockade of a waterway that normally carries about one-fifth of the world’s petroleum liquids.

The announcement came on the heels of roughly 21 hours of face-to-face talks in Islamabad between delegations led by Vice President J.D. Vance and Iranian Parliament Speaker Mohammad Bagher Qalibaf. Those negotiations, hosted by Pakistan, ended late Saturday or early Sunday without a final agreement to extend a fragile cease-fire or fully reopen the strait.

That failure marked a turning point in a conflict that began Feb. 28, when large-scale U.S. and Israeli strikes on Iran triggered wider fighting and prompted Tehran to lay mines and threaten shipping near the Strait of Hormuz. By early March, tanker traffic through the narrow channel between Oman and Iran had largely collapsed, leading to what international energy agencies described as a historic oil supply shock and a coordinated release of about 400 million barrels from strategic reserves.

Against that backdrop, the U.S. military had already started moving to reopen the waterway. On April 11, U.S. Central Command, which oversees forces in the Middle East, said its units “began setting conditions for clearing mines in the Strait of Hormuz.” The command said two guided-missile destroyers, USS Frank E. Peterson Jr. and USS Michael Murphy, had transited the strait and operated in the Arabian Gulf as part of the effort.

“Today, we began the process of establishing a new passage and we will share this safe pathway with the maritime industry soon to encourage the free flow of commerce,” Adm. Brad Cooper, the commander of U.S. Naval Forces Central Command, said in a statement. The command added that additional U.S. forces, including underwater drones, would join the clearance mission in the coming days.

So far, however, neither the Pentagon nor the State Department has published a formal blockade declaration or detailed rules for how U.S. forces will treat commercial vessels in and around Hormuz. There has been no public clarification of the geographic boundaries of the interdiction Trump described, how the United States intends to determine whether a ship has paid Iran, or how neutral-flagged merchant ships will be handled.

Those gaps matter to shipowners, insurers and allied governments trying to assess whether the president’s language marks a change in legal status for the waterway or mainly a political signal layered onto the existing mine-clearance operation.

Before the current conflict, roughly 20 million barrels per day of crude oil and petroleum liquids moved through the Strait of Hormuz, according to data used by the U.S. Energy Information Administration and the International Energy Agency. That flow — nearly 20% of global petroleum liquids consumption — underpins government budgets in Persian Gulf states and fuels power plants, vehicles and industry from Europe to East Asia.

The effective shutdown of that route in March helped drive up prices and forced major importers to tap emergency stocks. A renewed disruption, particularly one involving armed interdictions on the high seas, could again push up energy costs and ripple through inflation and economic growth.

Trump’s Truth Social post targeted not only Iran’s military actions but also its efforts to charge what he called “tolls” on shipping. Tehran has sought to leverage its control of waters bordering the strait to pressure foreign governments and extract payments as traffic has resumed under the Pakistan-brokered two-week cease-fire announced April 8.

International law sets out conditions for a lawful naval blockade. Under widely cited guidelines such as the San Remo Manual on the Law of Naval Warfare, a belligerent that imposes a blockade must declare and notify it, enforce it effectively and apply it impartially to all vessels of all states. A blockade cannot have the sole purpose of starving the civilian population or denying it essential supplies, and it must in many circumstances allow humanitarian relief.

The United Nations Convention on the Law of the Sea, a global treaty that governs the use of oceans and seas, also recognizes a special regime of “transit passage” for straits used for international navigation, such as Hormuz. That regime is meant to guarantee ships and aircraft of all countries the right to pass through straits without hindrance, subject to certain rules.

As of Sunday, there was no indication that the U.S. had lodged a formal blockade notice with the United Nations or international maritime bodies, or that any international court or the U.N. Security Council had weighed in. Trump also wrote that “other countries will also be involved,” according to reports on his post, but no allied government had publicly signed onto a joint blockade or interdiction campaign.

Any extended naval operation in and around Hormuz is likely to intersect with domestic U.S. war powers debates as well. Under the War Powers Resolution of 1973, presidents are expected to notify Congress within 48 hours of introducing U.S. forces into hostilities and face a 60-day clock for unauthorized deployments, though administrations have interpreted those requirements differently. A long-running blockade, particularly if it leads to clashes with Iranian forces or the detention of foreign-flagged ships, could draw scrutiny from lawmakers.

The operational environment is fraught even without a declared blockade. Iranian minefields, fast-attack boats and drones complicate efforts to clear and safely mark shipping lanes. Commercial captains must weigh not only Iranian threats but also the prospect of U.S. boarding or diversion if their cargoes or business ties raise suspicion.

In the coming days, governments and markets will be watching for several concrete signals: whether the White House, Pentagon or State Department issues a written blockade declaration and map; whether the Navy publishes guidance to commercial shippers; how Iran’s military, particularly the Islamic Revolutionary Guard Corps Navy, responds; and whether oil prices and shipping insurance premiums spike as trading opens.

For now, the United States has publicly committed to establishing a “safe pathway” through one of the world’s most contested waterways at the same moment its president is threatening to block “any and all” ships that try to use it. How that tension is resolved will determine whether the Strait of Hormuz inches back toward normal traffic — or becomes the center of a broader confrontation at sea.