The United States military launched a blockade of all Iranian ports and coastal areas on Monday after weekend negotiations in Pakistan ended without a deal, sharply escalating a conflict that has already upended global energy markets and drawn alarm from allies and international institutions. US Central Command announced the blockade would take effect at 10am Washington time, targeting all vessels entering or departing Iranian ports on the Gulf and Gulf of Oman — a move that analysts say could cost Iran an estimated $435 million a day in lost trade.

The breakdown came after 21 hours of talks in Islamabad between American and Iranian negotiators, including Vice President JD Vance, Special Envoy Steve Witkoff, and Jared Kushner on the US side. A central sticking point was Iran's nuclear programme: Washington is demanding Tehran hand over or sell its stockpile of highly enriched uranium, while Iran has sought war reparations and the unfreezing of roughly $27 billion in Iranian assets. Vance said the US did not see a "fundamental commitment of will" from Tehran to abandon its nuclear ambitions. Iran's lead negotiator, parliamentary speaker Mohammad Bagher Ghalibaf, accused Washington of "excessive" demands and said the US had "failed to win Iran's trust." President Trump, responding to reporters in Maryland, was dismissive of further diplomacy: "I don't care if they come back or not. If they don't come back, I'm fine."

The Strait of Hormuz — a narrow waterway between Iran and Oman through which roughly one-fifth of the world's oil and natural gas normally flows — has already been severely disrupted since the conflict began on 28 February, with Iran effectively blockading non-approved traffic. Iran's Revolutionary Guards warned that any military vessels approaching the strait would be considered a ceasefire violation and met with a "harsh and decisive" response. Iran's military called the US action an "act of piracy," asserting that the ports of the Gulf and Gulf of Oman are "either for everyone or for no one." Two US Navy guided-missile destroyers were already in the strait over the weekend conducting minesweeping operations, as Iran is believed to have deployed mines throughout portions of the waterway.

The economic consequences are already rippling outward. Oil prices surged above $100 a barrel on Monday — US crude rising 8% to $104 and Brent crude up 7% to $102 — while shipping data provider Lloyd's List Intelligence reported that all traffic through the strait halted following Trump's announcement. Iran currently exports approximately 1.84 million barrels of oil per day, and a blockade would remove that supply from world markets. The UN Development Programme warned in a separate report that the ongoing conflict risks plunging more than 32 million people worldwide into poverty through what it called a "triple shock" of higher energy costs, food insecurity, and slower economic growth.

Allies have been guarded in their response. UK Prime Minister Keir Starmer said Britain would not participate in the blockade and was focused solely on restoring free navigation through the strait, adding that the UK would not "get dragged into the war." Australia called for full reopening of the waterway and a swift return to negotiations. Pope Leo XIV — the first American-born pope — urged political leaders to "stop and negotiate peace," drawing a fierce rebuke from Trump, who called the pontiff "weak on crime and terrible for foreign policy." The pope, travelling to Algeria, said simply: "I am not a politician. I have no intention to debate with him." The two-week ceasefire between Washington and Tehran is due to expire on 22 April, and officials have not ruled out returning to talks before that deadline, though the launch of the blockade has significantly raised the stakes on both sides.