Britain announced Monday it will join the United States in the mission to protect merchant vessels in the Arabian Gulf amid heightened tensions with Iran. London’s decision to form the joint maritime taskforce with the United States marks a departure in policy under new Prime Minister Boris Johnson, after efforts under his predecessor Theresa May to form a European-led grouping. It follows a spate of incidents -- including the seizure of ships -- between Iran and Western powers, in particular Britain and the US, centered on the vital Strait of Hormuz thoroughfare. "The UK is determined to ensure her shipping is protected from unlawful threats, and for that reason we have today joined the new maritime security mission in the Gulf," Defense Secretary Ben Wallace said in a statement. “It is vital to secure the freedom for all international shipping to navigate the Strait of Hormuz without delay, given the increased threat,” he added. “The deployment of 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.” The announcement from Britains defense ministry did not detail which, if any, other countries would be joining the new naval coalition. No other nations are yet involved. Britain was also at pains to stress that it had not changed its broader policy towards Tehran. "We remain committed to working with Iran and our international partners to de-escalate the situation and maintain the nuclear deal," Foreign Secretary Dominic Raab said. A British source said the focus of the new mission would be protecting the security of shipping and Britain would not be joining US sanctions against Iran, reported Reuters. Another British source said London hoped the US-led mission would transition toward a European-led mission. The United Kingdom has also offered to lead one of the US-led mission’s maritime task groups. Britain has deployed a destroyer HMS Duncan and a frigate HMS Montrose to the Gulf to accompany UK-flagged vessels through the strait. So far, 47 ships have been accompanied by the naval vessels, British officials said. Later this year, another Type 23 Frigate, HMS Kent, will take over from HMS Duncan, while HMS Montrose completes planned maintenance. HMS Montrose will remain stationed in the Middle East until 2022. London’s announcement came hours after Iranian Foreign Minister Mohammad Javad Zarif said Washington was increasingly isolated in its hardline stance against Tehran and its allies were too "ashamed" to join its forces in the Gulf. He also dismissed US calls for talks as a sham, confirming he had turned down an offer to meet President Donald Trump last month despite the threat of US sanctions against him. "Today the United States is alone in the world and cannot create a coalition," he said. Tehran and Washington have been locked in a battle of nerves since last year when Trump withdrew the US from a landmark 2015 deal placing curbs on Irans nuclear program and began reimposing sanctions. Tensions have spiked since the Trump administration began stepping up a campaign of "maximum pressure" against Iran. Drones have been downed and tankers seized by Iranian authorities or mysteriously attacked in Gulf waters, while Britain has detained an Iranian tanker off Gibraltar. Germany said Monday it was currently "not in favor" of joining an American-led coalition. Meanwhile the US continues to target Iran economically, while holding out the prospect of possible talks. It imposed sanctions against Zarif on Wednesday --under the same sanctions already applied to supreme leader Ali Khamenei -- targeting any assets he has in America and squeezing his ability to travel.