The expansion of the "logistics hub" at Duqm will "facilitate Royal Navy deployments to the Indian Ocean" and "further support British Army training in Oman," the Ministry of Defence said.

"The long-standing friendships between the UK and the Gulf states are more important than ever," said Defence Secretary Ben Wallace as he visited Oman and Qatar.

"Whether tackling Daesh (the so-called Islamic State group), or making our streets in the UK safer thanks to our intelligence networks, these are hugely valuable relationships that I am pleased to be able to renew this week," he added.

The port has a dry dock facility which could support Britain's two aircraft carriers, HMS Queen Elizabeth and HMS Prince of Wales, the ministry said.

Britain sent warships to the Gulf last year to escort freight vessels after Iranian Revolutionary Guards stormed and detained the UK-flagged Stena Impero and its 23 crew as they sailed through the Strait of Hormuz.