Other US allies criticise Trump’s move, including France, Spain and Turkiye, and China also condemns the plan.

British Prime Minister Keir Starmer says his country will not join the blockade of the Strait of Hormuz announced by United States President Donald Trump, a move also criticised by other US allies.

“We are not supporting the blockade,” Starmer told BBC radio on Monday, adding that the United Kingdom “is not getting dragged in” to the US-Israel war on Iran.

Starmer said it was vital to get the strait reopened. In peacetime, about 20 percent of the world’s oil supplies pass through the strategic waterway that links the Gulf to the Indian Ocean.

“It is in my view vital that we get the strait open and fully open, and that’s where we’ve put all of our efforts in the last few weeks, and we’ll continue to do so,” he said.

Al Jazeera’s Rory Challands, reporting from London, said Starmer has continued to “maintain a delicate balancing act” of saying the UK will not be joining the war while being careful not to level any criticism directly at Trump regarding his actions in the war.

Traffic through the strait has been heavily restricted since the start of the war. Iran has allowed through only some vessels serving friendly countries, such as China.

Starmer made his statement as the US military announced it would block all maritime traffic entering and exiting Iranian ports starting from 14:00 GMT. It was unclear, however, how the US military would enforce the blockade.

“The blockade will be enforced impartially against vessels of all nations entering or departing Iranian ports and coastal areas, including all Iranian ports on the Arabian Gulf and Gulf of Oman,” the US military’s Central Command said.

US forces would not impede vessels transiting the Strait of Hormuz to and from non-Iranian ports, it added.

In a lengthy social media post on Sunday, Trump said his goal was to clear the strait of mines and reopen it to all shipping and Iran must not be allowed to profit from controlling the waterway.

Meanwhile, French President Emmanuel Macron announced that France and the UK would hold a conference in the coming days aimed at restoring freedom of navigation in the strait.

Macron reiterated that no diplomatic effort be spared in reaching a lasting end to the US-Israel war on Iran.

Nicole Grajewski, assistant professor at the Center for International Research at the Paris Institute of Political Studies, said a US blockade was “not a minor coercive signal” but could rather be considered essentially a resumption of the war.

Other US allies also criticised Trump’s move, including Spanish Defence Minister Margarita Robles, who said the planned naval blockade “makes no sense”.

“It’s one more episode in this whole downward spiral into which we’ve been dragged,” she said.

Fellow NATO ally Turkiye said the Strait of Hormuz should open “as soon as possible”.

“Negotiations with Iran should be conducted, persuasion methods should be used and the strait should be opened as soon as possible,” Turkish Foreign Minister Hakan Fidan told the state-run Anadolu news agency.

China, Washington’s great power rival and a big importer of Iranian oil, also criticised the plan.

“The Strait of Hormuz is an important international trade route for goods and energy, and maintaining its security, stability and unimpeded flow is in the common interest of the international community,” Ministry of Foreign Affairs spokesman Guo Jiakun said, urging Iran and the US not to reignite the war.