The UK said it would contribute autonomous mine-hunting equipment, Typhoon fighter jets and the warship HMS Dragon to a multinational defensive mission aimed at securing shipping in the Strait of Hormuz.
Defence Secretary John Healey announced the commitment during an online summit involving more than 40 defence ministers.
The Iran war has drastically reduced traffic through the strait, disrupting oil exports and leading to soaring energy prices.
"With our allies, this multinational mission will be defensive, independent and credible," he said.
The UK's contribution will be backed by £115 million ($155.6 million) of funding for mine-hunting drones and counter-drone systems, as London seeks to reassure commercial shipping of its commitment to freedom of navigation amid heightened regional tensions.
The package will include autonomous systems to detect and clear sea mines. It will also include high-speed drone boats, Typhoon jets and the HMS Dragon, an air defence destroyer that is already on its way to the Middle East.
Britain has more than 1,000 personnel in the region as part of existing defensive operations, including counter-drone teams and fast plane squadrons.
France moved its Charles de Gaulle aircraft carrier from the Mediterranean to the Red Sea on Wednesday in a bid to show the US and Iran it was willing to help solve the Hormuz crisis.
US President Donald Trump has suggested he is willing to oversee a lengthy blockade of the strait. An extended blockade would risk further damage to the global economy. The US government assumes it will remain effectively shut until at least late May, a forecast by the Energy Information Administration has shown.
