At a two-day meeting in London, military planners discussed the practicalities of a multinational mission led by the UK and France to protect navigation in the key waterway following a sustainable ceasefire, top defence officials said.

The aim is to form a "defensive, multinational mission that will strengthen the confidence of commercial shipping, and, if necessary, clear mines and protect vessels when the hostilities end", British defence minister John Healey said.

The British ministry said the meeting involved more than 44 countries from every continent.

Healey and French counterpart Catherine Vautrin said in a joint statement they were "confident that real progress can be made".

"International trade, energy, and economic stability for all our nations depend on freedom of navigation" in the strait, Healey told those attending.

He called for "practical military plans", saying "millions of people" were relying on a successful outcome from the meeting.

"We can't let them down," he said.

British Prime Minister Keir Starmer has said more than a dozen countries have agreed to participate in the mission to free up navigation in Hormuz.

Iran said on Wednesday it would not reopen the Strait of Hormuz as long as the United States continued to blockade Iranian ports.

While strikes around the region have mostly stopped since the start of a ceasefire, the US and Iran have continued to exert pressure around the trade route.

Before the war started on February 28, about a fifth of the world's oil was shipped through the Strait.