UK PRIME MINISTER Keir Starmer has refused to join Donald Trump’s blockade of the Strait of Hormuz, which could compound economic pain with higher petrol costs.

The US president threatened to stop tankers from entering or leaving the key oil and gas shipping lane, a move that is expected to further drive up oil prices when markets open, after they have already risen as a result of Iran’s grip on the strait in retaliation for the US-Israel war against it.

UK Chancellor Rachel Reeves will travel to Washington for International Monetary Fund meetings this week, after warning that “the war in Iran will come at a cost to British families and business”.

Starmer’s decision comes as UK MPs return to Westminster from the Easter recess today with no resolution to the Middle East crisis in sight and the fate of a shaky two-week ceasefire uncertain.

Trump announced the shipping blockade after US-Iranian peace talks in Pakistan ended without a deal, with both sides blaming each other.

The American leader said on his Truth Social platform that the US military would start “blockading any and all ships trying to enter, or leave, the Strait of Hormuz” from 10am US Eastern Time.

Trump added, without elaborating: “Other Countries will be involved with this Blockade.”

Britain will not be involved, it is understood.

The UK is “urgently working with France and other partners to put together a wide coalition to protect freedom of navigation,” a Government spokesperson said.

Starmer and French President Emmanuel Macron agreed on the need to work with a broad coalition of partners on the matter in a call, according to No 10.

Britain will host further talks on reopening the maritime pinch-point with a coalition of countries this week.

The third such meeting convened by the UK is expected to look for ways to support a sustainable end to the conflict and focus on increasing international diplomatic pressure on Iran to reopen the strait, including through sanctions.

Starmer’s call with Macron yesterday took place before Trump posted on social media about a blockade, it is understood.

Trump told Fox News “the UK and a couple of other countries are sending mine sweepers” to the strait, and “it won’t take long to clean it out”.

The Prime Minister previously said UK mine hunting systems were already in the region. But this is thought to refer to minesweeping drones which could be deployed once the situation stabilises, and to be distinct from Trump’s blockade.

US Central Command, which is responsible for American military operations in the Middle East, said its blockade of Iranian ports would begin today.

US forces “will not impede freedom of navigation for vessels transiting the Strait of Hormuz to and from non-Iranian ports,” the military said in a statement that appeared to contradict Trump’s threat to stop all ships.

The president blamed the failure of negotiations on Iran’s refusal to reopen the channel and commit to giving up its nuclear ambitions.

Iran’s foreign minister Abbas Araghchi accused Washington of “maximalism, shifting goalposts, and blockade,” adding: “Enmity begets enmity.”

Trump has also renewed his war-of-words with Pope Leo XIV, who previously criticised the president’s rhetoric regarding the conflict.

In a post on Truth Social early on Monday, Trump said: “Pope Leo is WEAK on Crime, and terrible for Foreign Policy… I don’t want a Pope who thinks it’s OK for Iran to have a Nuclear Weapon.”