The UK is looking at "any options" - including working with US and allies - to secure key oil shipping routes through the Strait of Hormuz, Ed Miliband has said.
It comes after the US President Donald Trump on Saturday threatened to open the channel "one way or another" and urged countries including China, France and the UK to send warships to the waterway.
The Energy Secretary told the BBC's it was "very important" that the strait was made safe for shipping, but refused to give details of options considered by the government.
Iran's effective blockage of the Strait, one of the world's most important shipping channels, has had a catastrophic impact on global supply chains and energy prices.
Iran's new Supreme Leader Mojtaba Khameini has vowed to keep blocking the strait as a means of political and economic pressure against the US. About 20% of the world's oil usually passes through the strait.
