Britain is in talks with allies on how to reopen the Strait of Hormuz for hundreds of tankers to pass through, says Foreign Secretary Yvette Cooper.
At a meeting of foreign ministers near Paris on Friday, she stressed that the Tehran regime could not be allowed to keep the “world economy hostage”.
Earlier, a Thai tanker reportedly ran aground after being hit and set on fire weeks ago as it attempted to transit the key strait, through which a fifth of global oil supplies are transported.
Tehran is allowing some tankers, including from India and China, to go through the waterway without coming under attack.
But Iran has warned that British and other western vessels will be targeted.
More than a dozen tankers have been hit since the start of the conflict, triggering the biggest ever oil supply shock.
The Thai-flagged cargo ship Mayuree Naree ran aground after it came under attack more than a fortnight ago from Iran in the strait and was abandoned by its crew, Iranian media reported Friday.
Thailand's Foreign Ministry said Friday that the Iranian and Omani authorities were able to reach the Mayuree Naree on a rescue mission as three sailors remain unaccounted for.
The ship came under attack on March 11.
The semi-official Tasnim and Fars news agencies, believed to be close to Iran's paramilitary Revolutionary Guard, reported that the ship ran aground near the village of Ramchah on Qeshm.
The blockade of the strait is causing economic carnage in the UK with a £15 billion blow to GDP and inflation spiralling to towards 4%.
Speaking at the G7 meeting in Vaux-de-Cernay, Ms Cooper said: “Iran cannot be able to just hold the global economy hostage as a result of a strait which is about international shipping routes and the freedom of navigation that has been so strongly supported at the United Nations, but also by countries across the world.”
She added that she was “deeply concerned” about Russia's co-operation with Iran as she sought to maintain pressure on President Vladimir Putin over his invasion of Ukraine despite the crisis in the Gulf.
Ms Cooper said drones provided to Russia by Iran have been involved in strikes in Ukraine, “but we have also seen support from Russia provided to Iran in the Middle East conflict as well”.
Britain, France, Germany, Australia and other allies have rejected Donald Trump’s demand to send warships for a maritime battle to re-open the strait, with the US president lashing out at the UK by describing its aircraft carriers as “toys”.
But these nations and others are ready to joint a mission to keep open the strait once the conflict de-escalates.
Thousands of US Marines, though, are being deployed to the region amid claims that Trump wants to dramatically ramp up the war and then claim victory.
As they were heading to the Middle East, the president extended his deadline for Iran to reopen the Strait of Hormuz, or face the destruction of its energy plants, for 10 days.
The move came after Tehran rejected his 15-point proposal to end the war he launched with Israel.
Iran gave no direct indication that it was ready for negotiation or compromise, although senior officials have said diplomacy continues.
The Islamic Revolutionary Guard Corps reaffirmed that all shipping "to and from ports of allies and supporters of the Israeli-American enemies" to any destination was prohibited.
It also urged civilians across the Middle East, where it has already attacked countries hosting US bases, to vacate areas near U.S. bases, Iran's Mehr news agency reported.
Israeli Defence Minister Israel Katz said Tehran had continued to fire missiles toward civilian areas in Israel, and therefore Israel's attacks on Iran "will escalate and expand to additional targets".
The war has spread across the Middle East, killing thousands of people.
