A billboard with a graphic design about the Strait of Hormuz on a building in Tehran, Iran, April 13, 2026. Photo: Majid Asgaripour/WANA (West Asia News Agency) via REUTERS

The US military began a blockade of ships leaving Iran’s ports on Monday, President Donald Trump said, and Tehran threatened to retaliate against its Gulf neighbors’ ports after weekend talks in Islamabad on ending the war broke down.

A US official said there was continued engagement with Iran, and forward motion on trying to get to an agreement. Pakistani Prime Minister Shehbaz Sharif also said efforts were still under way to resolve the conflict.

But oil prices climbed back over $100 per barrel, with no sign of a swift reopening of the Strait of Hormuz to ease the biggest ever disruption in supplies and broader concerns over the durability of a two-week ceasefire agreement reached last week.

Trump said Iran had been in touch on Monday and wanted to make a deal but that he would not sanction any agreement allowing Tehran to have a nuclear weapon.

“Iran will not have a nuclear weapon,” Trump told reporters at the White House. “We can’t let a country blackmail or extort the world.”

Since the United States and Israel began the war on Feb. 28, Iran effectively shut the Strait of Hormuz to all vessels except its own, saying passage would be permitted only under Iranian control and subject to a fee.

Trump has said Washington would block Iranian vessels and any ships that paid such tolls and that any Iranian “fast-attack” ships that went near the blockade would be eliminated.

Brigadier General Reza Talaei-Nik, a spokesperson for Iran’s Ministry of Defense, warned that foreign military efforts to police the strait would escalate the crisis and instability in global energy security.

NATO allies including Britain and France said they would not be drawn into the conflict by taking part in the blockade, stressing instead the need to reopen the waterway, through which about one-fifth of the world’s oil normally passes.

CEASEFIRE UNDER STRAIN

The ceasefire that halted six weeks of US and Israeli airstrikes looked in jeopardy, with only a week left to run. Washington said Tehran rejected its demands at weekend talks in Islamabad, the highest-level discussions between the two nations since Iran’s 1979 Islamic Revolution.

The US military’s Central Command said the blockade would be “enforced impartially against vessels of all nations” entering or leaving Iranian ports in the Gulf and Gulf of Oman.

“The blockade will not impede neutral transit passage through the Strait of Hormuz to or from non-Iranian destinations,” Central Command said in a note to seafarers seen by Reuters on Monday.

Two Iranian-linked tankers, the Aurora and New Future, left the strait laden with oil products on Monday before the deadline, according to LSEG data.

An Iranian military spokesperson called any US restrictions on international shipping “piracy,” warning that if Iranian ports were threatened, no port in the Gulf or Gulf of Oman would be secure. Any military vessels approaching the strait would violate the ceasefire, Iran’s Revolutionary Guards said.

Trump said Iran’s navy had been “completely obliterated” during the war, adding that only a small number of “fast-attack ships” remained.

“Warning: 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. It is quick and brutal,” Trump, much of whose communications are on social media, wrote on his Truth Social site.

He was apparently referring to the US strikes carried out against suspected drug boats in the Caribbean and Pacific. The strikes, which began in September, killed more than 160 people.

LEBANON FACES ATTACKS

Trump has also lashed out at US-born Pope Leo, who has spoken out against the war, denouncing him as “terrible” in a rare direct attack by a US president on a pontiff.

With rising energy prices causing political blowback, Trump paused the US-Israeli bombing campaign last week after threatening to destroy Iran’s “whole civilization” unless it reopened the strait.

Israel has continued to bombard Lebanon and on Monday Israeli troops launched an attack it said was intended to seize a key south Lebanon town from Iran-backed terrorist group Hezbollah. Israel and ‌the US have ⁠said the campaign against Hezbollah was not part of the ceasefire, while Iran has insisted it is.

Iran has brought new demands, including recognition of its control of the waterway, lifting of sanctions, and the withdrawal of forces from US military bases across the Middle East.

Trump has declared victory, despite so far not fully achieving the objectives he set out at the start of the war: to eliminate Iran’s ability to strike its neighbors, end its nuclear program, and make it easier for Iranians to topple their government.

Benchmark oil prices, which had eased last week after the ceasefire was announced, traded around 6% higher on Monday, off the day’s peaks but still above $100 a barrel.

Traders say the main benchmarks – used to set prices for trillions of dollars’ worth of commodities worldwide – actually understate the severity of a disruption with no precedent in modern times.