Britain is joining the US in a naval mission in the Gulf to protect international shipping following tanker seizures by the Iranian military, a move that reflects the escalating security crisis in the region.

Two Royal Navy warships already in the area will be working alongside two US ships to accompany vessels through the Strait of Hormuz, which carries 20 per cent of the world’s oil supplies.

Whitehall officials insist the mission will not remain under US control and, in time, will transition to one with European command in which the UK has offered to lead one of the maritime task groups.

The British government will not change its stance towards Iran and will back, not follow, Donald Trump’s administration, ministers insisted.

London continues to stand by Tehran’s agreement with international powers, they stressed, and will not follow the US in imposing sanctions against Iran.

In photos: British-flagged tanker seized by Iran Show all 13 1 /13 In photos: British-flagged tanker seized by Iran In photos: British-flagged tanker seized by Iran A speedboat of Iran's Revolutionary Guard moving around the British-flagged oil tanker Stena Impero Tasnim News Agency/AP In photos: British-flagged tanker seized by Iran Crew members of the British-flagged tanker Stena Impero, that was seized by Iran in the Strait of Hormuz EPA/IRIB News Agency In photos: British-flagged tanker seized by Iran A satellite image of the Iranian port city of Bandar Abbas reveals the presence of the seized British oil tanker, the Stena Impero on July 22 Maxar Technologies/Reuters In photos: British-flagged tanker seized by Iran Iranian Revolutionary Guard Corps (IRGC) claims to have seized Stena Impero at the Strait of Hormuz with 23 crew on board on 20 July EPA/IRIB News Agency In photos: British-flagged tanker seized by Iran Iranian Revolutionary Guards patrolling around the captured British-flagged tanker Stena Impero as it's anchored off the Iranian port city of Bandar Abbas AFP/Getty In photos: British-flagged tanker seized by Iran epa07733612 A handout photo made available by Iranian state-run IRIB News Agency on 22 July 2019 shows crew members of the British-flagged tanker Stena Impero, that was seized by Iran in the Strait of Hormuz on 19 July 2019. Iranian Revolutionary Guard Corps (IRGC) claims to have seized Stena Impero at the Strait of Hormuz with 23 crew on board on 20 July 2019. EPA/IRIB NEWS AGENCY / HANDOUT HANDOUT EDITORIAL USE ONLY/NO SALES IRIB NEWS AGENCY / HANDOUT EPA/IRIB News Agency In photos: British-flagged tanker seized by Iran A satellite image of the Iranian port city of Bandar Abbas reveals the presence of the seized British oil tanker, the Stena Impero on July 22 Maxar Technologies/Reuters In photos: British-flagged tanker seized by Iran A speedboat of the Iran's Revolutionary Guard moves around a British-flagged oil tanker Stena Impero AP In photos: British-flagged tanker seized by Iran epa07733614 A handout photo made available by Iranian state-run IRIB News Agency on 22 July 2019 shows crew members of the British-flagged tanker Stena Impero, that was seized by Iran in the Strait of Hormuz on 19 July 2019. Iranian Revolutionary Guard Corps (IRGC) claims to have seized Stena Impero at the Strait of Hormuz with 23 crew on board on 20 July 2019. EPA/IRIB NEWS AGENCY / HANDOUT HANDOUT EDITORIAL USE ONLY/NO SALES IRIB NEWS AGENCY / HANDOUT EPA/IRIB News Agency In photos: British-flagged tanker seized by Iran In this photo released by state-run IRIB News Agency, which aired on Monday, July 22, 2019, shows cooks in the galley of the British-flagged tanker Stena Impero that was seized by Tehran in the Strait of Hormuz on Friday. The Associated Press cannot independently verify the condition of the crew members, but in the video they looked to be in good health and it didn't appear as though they were being filmed under duress. (IRIB News Agency via AP) AP In photos: British-flagged tanker seized by Iran epa07733619 A handout photo made available by Iranian state-run IRIB News Agency on 22 July 2019 shows crew members of the British-flagged tanker Stena Impero, that was seized by Iran in the Strait of Hormuz on 19 July 2019. Iranian Revolutionary Guard Corps (IRGC) claims to have seized Stena Impero at the Strait of Hormuz with 23 crew on board on 20 July 2019. EPA/IRIB NEWS AGENCY / HANDOUT HANDOUT EDITORIAL USE ONLY/NO SALES IRIB NEWS AGENCY / HANDOUT EPA/IRIB News Agency In photos: British-flagged tanker seized by Iran epa07733613 A handout photo made available by Iranian state-run IRIB News Agency on 22 July 2019 shows crew members of the British-flagged tanker Stena Impero, that was seized by Iran in the Strait of Hormuz on 19 July 2019. Iranian Revolutionary Guard Corps (IRGC) claims to have seized Stena Impero at the Strait of Hormuz with 23 crew on board on 20 July 2019. EPA/IRIB NEWS AGENCY / HANDOUT HANDOUT EDITORIAL USE ONLY/NO SALES IRIB NEWS AGENCY / HANDOUT EPA/IRIB News Agency In photos: British-flagged tanker seized by Iran epa07733616 A handout photo made available by Iranian state-run IRIB News Agency on 22 July 2019 shows crew members of the British-flagged tanker Stena Impero, that was seized by Iran in the Strait of Hormuz on 19 July 2019. Iranian Revolutionary Guard Corps (IRGC) claims to have seized Stena Impero at the Strait of Hormuz with 23 crew on board on 20 July 2019. EPA/IRIB NEWS AGENCY / HANDOUT HANDOUT EDITORIAL USE ONLY/NO SALES IRIB NEWS AGENCY / HANDOUT EPA/IRIB News Agency

No other European power, however, has joined the American and British naval initiative so far and the only other European warship in the waters, a French frigate, will continue to operate autonomously.

British government sources stated that talks have been held with a number of European allies and a number have expressed an interest in joining a future European commanded operation.

But some western states, including France and Germany, have expressed unwillingness to join a task force led by the US.

The British decision to join the mission comes three weeks after a British-flagged tanker, Stena Impero, was taken over by Iran’s Revolutionary Guards. That followed the capture of an Iranian-owned tanker, Grace 1, by Royal Marines off Gibraltar.

Two British frigates in the Gulf, the destroyer HMS Duncan and frigate HMS Montrose, will continue to accompany UK-flagged and international shipping and two American cruiser-destroyers, stationed at each end of the Strait of Hormuz, will protect British ships when called upon.

The two countries will, however, operate, for the time being, under different rules of engagement.

Iran's Revolutionary Guards publish purported exchange with British warship

Ben Wallace, the defence secretary, said: “The UK is determined to ensure her shipping is protected from unlawful threats and for that reason we have joined the new maritime security mission in the Gulf.

“The deployment of the Royal Navy assets is a sign of our commitment to our UK-flagged vessels and we look forward to working alongside the US and others to find an international solution to the problems in the Strait of Hormuz.”

Dominic Raab, the foreign secretary, added : “It is vital to secure the freedom for all international shipping to navigate the Strait of Hormuz without delay, given the increased threat. This deployment will reinforce security and provide reassurance for shipping. Our aim is to build the broadest international support to uphold freedom of navigation in the region, as protected under international law.

“Our approach to Iran hasn’t changed. We remain committed to working with Iran and our international partners to de-escalate the situation and maintain the nuclear deal.”

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Iran has, however, repeatedly complained about the British seizure of Grace 1 and demanded the release of its crew and cargo.