Britain has called for a European-led naval mission to ensure safe shipping through the Strait of Hormuz, days after Iran seized a British-flagged tanker in what London described as an act of "state piracy".
Foreign Secretary Jeremy Hunt outlined the plans to parliament after a meeting of COBR, the government's emergency committee, which discussed London's response to Friday's capture of the Stena Impero tanker by Iranian commandos at sea.
"Under international law, Iran had no right to obstruct the ship's passage - let alone board her. It was, therefore, an act of state piracy," Mr Hunt told parliament on Monday.
"We will now seek to put together a European-led maritime protection mission to support safe passage of both crew and cargo in this vital region," Mr Hunt said.
The British announcement signals a potential shift from Washington's major European allies who so far have been cool to the US requests that they beef up their military presence in the Gulf, for fear of feeding the confrontation there.
Nevertheless, Mr Hunt made a point of saying that the proposal would not involve contributing European military power to back Washington's hardline stance against Iran.
Washington's major European allies Britain, France and Germany all opposed a decision last year by US President Donald Trump to abandon an international agreement that promised Iran access to trade in return for accepting curbs on its nuclear program.
The new mission "will not be part of the US maximum pressure policy on Iran because we remain committed to preserving the Iran nuclear agreement", Mr Hunt said.
The Europeans have tried to stay neutral as tension has risen between Tehran and Washington.
But Britain was plunged directly into the crisis on 4 July when it seized an Iranian tanker off Gibraltar accused of violating sanctions on Syria.
Iran repeatedly threatened to retaliate, culminating with its seizure of the Stena Impero on Friday using the same tactics - commandos rappelling to the deck from helicopters - that British Royal Marines had used aboard Iran's own ship.
The US has an aircraft carrier strike group in the Gulf and a navy that is far more powerful than those of all its European allies put together.
But it has made a point in recent weeks of saying it cannot protect shipping on its own, and US Secretary of State Mike Pompeo reiterated this position on Monday.
"The responsibility ... falls to the United Kingdom to take care of their ships," he said.
Earlier Iran's state broadcaster aired a video showing the 23-member crew of the Stena Impero.
They were seen dressed in red uniforms and seated around a table on board the vessel as an unidentified Iranian man is heard thanking them for their co-operation.
The footage came as the Iranian embassy in India said all crew members were safe and still on the vessel.
Eighteen of the Stena Impero's 23-strong crew are Indian nationals, Iranian authorities said previously.
The crew also includes Filipino, Russian and Latvian nationals.
