Cairo, 13 April  

The US military announced it will begin a blockade of all Iranian ports and coastal areas on Monday, as President Donald Trump sought to pressure Iran in a move that risks driving oil prices even higher and renewing the war.

The announcement set the stage for a showdown, as Iran immediately responded with threats on all ports in the Persian Gulf and the Gulf of Oman.

“Security inthe Persian Gulf and the Sea of Oman is either for everyone or for NO ONE,” the Islamic Republic of Iran Broadcasting reported Monday. “NO PORT in the region will be safe,” according to a statement from the Iranian military and the Revolutionary Guards.

US Central Command announced the blockade would begin on Monday at 10am EDT or 5.30pm in Iran, and would be “enforced impartially against vessels of all nations entering or departing Iranian ports and coastal areas, including all Iranian ports on the Arabian Gulf (Persian Gulf) and Gulf of Oman”.

CENTCOM said it would still allow ships travelling between non-Iranian ports to transit the strait, a step down from the president's earlier threat to blockade the entire strait.

The announcement of the blockade halted the limited ship traffic that resumed in the strait since the ceasefire, said an early report from Lloyd's List intelligence. Marine trackers say over 40 commercial ships have crossed since the start of the ceasefire, down from roughly 100 to 135 vessel passages per day before the war.

The move came after marathon US-Iran ceasefire talks in Pakistan ended without an agreement on Saturday. US Vice President JD Vance said the talks stalled after Iran refused to accept American terms to refrain from developing a nuclear weapon.

Iran has demanded compensation for damage caused by US-Israeli strikes that launched the war on 28 Feb, and the release of Iran's frozen assets.

Later Sunday, Trump extended his feud over the war with Pope Leo XIV, lashing out in a Truth Social post that called the Catholic leader “terrible on foreign policy”.

The extraordinary broadside came after Leo denounced the war and demanded that political leaders stop and negotiate peace.

The blockade is likely intended to add pressure on Iran, which has exported millions of barrels of oil since the war began, much of it likely carried by so-called “dark” transits that evade Western government sanctions and oversight.

Trump also hopes to undercut Iran's control over the Strait of Hormuz after demanding that it reopen the waterway where 20% of global oil transited before fighting began. A US blockade could further rattle global energy markets.

Oil prices rose in early market trading after the blockade announcement. The price of US crude rose 8% to $104.24 a barrel, and Brent crude oil, the international standard, rose 7% to $102.29. Brent crude cost roughly $70 per barrel before the war in late February.

UK Prime Minister Keir Starmer told BBC radio Monday that Britain will not be part of a US blockade of Iranian ports in response to the closing of the Strait of Hormuz and that Britain is “not getting dragged into the war”.

He said UK efforts remain focused on reopening the key shipping route, and that Britain might help with mine clearing in the waterway, but only after the fighting stops.

A chorus of top-ranking Iranian officials threatened retaliation. Mohsen Rezaei, a military adviser and a former Revolutionary Guard Commander, wrote on X that the country's armed forces had “major untouched levers” to counter a Hormuz blockade. He said Iran would not be coerced by “tweets and imaginary plans”.

Iranian parliament speaker, Mohammad Bagher Qalibaf, who led Iran's side in the talks, addressed Trump in a statement on his return to Iran: “If you fight, we will fight.”

Iran's Revolutionary Guard later said the strait remained under Iran's “full control” and was open for non-military vessels, but military ones would get a “forceful response,” two semi-official Iranian news agencies reported.

During the 21-hour talks this weekend in Pakistan, the US military said two destroyers had transited the strait ahead of mine-clearing work, a first since the war began. Iran denied it.

The face-to-face talks that ended early Sunday were the highest-level negotiations between the longtime rivals since the 1979 Islamic Revolution.

Trump said Tehran's nuclear ambitions were the core reason for the talks' failure. In comments to Fox News, he again threatened to strike civilian infrastructure if it didn't give up its nuclear programme.

“In one half of a day they wouldn't have one bridge standing, they wouldn't have one electric generating plant standing, and they're back in the stone ages,” Trump said.

Vice President JD Vance, who led the US side in the talks, said Washington would need "an affirmative commitment that they will not seek a nuclear weapon".

Iranian negotiators could not agree to all US “red lines”, said a US official who spoke on condition of anonymity because they were not authorised to describe positions on the record.

Those red lines included Iran never obtaining a nuclear weapon, ending uranium enrichment, dismantling major enrichment facilities and allowing retrieval of its highly enriched uranium, along with opening the Strait of Hormuz and ending funding for Hamas, Hezbollah and Houthi rebels.

Iranian officials said talks fell apart over two or three key issues, blaming what they called US overreach. Qalibaf, who noted progress in negotiations, said it was time for the United States “to decide whether it can gain our trust or not”.

Iran's foreign minister claimed that the US tanked the negotiations when they were within “inches” of an agreement, but did not provide evidence.

"We encountered maximalism, shifting goalposts, and blockade,” wrote Abbas Araghchi on X.

Neither Iran nor the US indicated what will happen after the ceasefire expires on 22 April.

Pakistani Foreign Minister Ishaq Dar said his country will try to facilitate a new dialogue in the coming days. Iran said it was open to continuing dialogue, state-run IRNA news agency reported.

Iran's nuclear programme was at the centre of tensions long before the US and Israel launched the war on Feb 28. The fighting has killed at least 3,000 people in Iran, 2,055 in Lebanon, 23 in Israel and more than a dozen in Gulf Arab states, and damaged infrastructure in half a dozen countries.

Tehran has long denied seeking nuclear weapons but insists on its right to a civilian nuclear programme. The landmark 2015 nuclear deal, which Trump later pulled the US out of, took well over a year of negotiations. Experts say Iran's stockpile of enriched uranium, though not weapons-grade, is only a short technical step away.