US President Donald Trump said on Tuesday that Britain's deal to cede sovereignty of the island of Diego Garcia in the Chagos Islands to Mauritius was an "act of total weakness," adding that it was "another in a very long line of national security reasons why Greenland has to be acquired."
The island of Diego Garcia houses a strategically important US-UK air base in the Indian Ocean.
Britain and Mauritius last year struck a deal to transfer sovereignty of the Chagos Islands to Mauritius, while allowing Britain to retain control of the air base under a long-term lease.
The deal had previously been supported by the US administration, which said when it was signed in May that it "welcomed" the agreement and commended efforts to secure the long-term operation of the joint military base.
UK minister says deal is best option
Trump wrote on his Truth Social account: "Shockingly, our 'brilliant' NATO Ally, the United Kingdom, is currently planning to give away the Island of Diego Garcia, the site of a vital US Military Base, to Mauritius, and to do so FOR NO REASON WHATSOEVER."
Trump said there was no doubt that "China and Russia have noticed this act" by Britain.
British senior minister Darren Jones said on Tuesday that the deal was the best option for the military base, allowing it to operate for the next 100 years.
"The treaty has already been signed," Jones told Times Radio, adding that it could not now be changed.
"The best way we believe for Britain to respond ... is convening around the world using our diplomatic heft and using the Prime Minister's relationship with the President to protect British interests," he added.
Britain's Prime Minister Keir Starmer has built a solid relationship with Trump, becoming the first leader to secure a deal to lower some tariffs, but their connection has been shaken in recent days by disagreement over Trump's approach to Greenland and, now, his comments on Diego Garcia.
Trump has previously said that the encroaching presence of China and Russia makes Greenland vital to US security interests, and repeatedly insisted he will settle for nothing less than ownership of Greenland.
Britain's deal with Mauritius was delayed after Trump's inauguration in January 2025, with London seeking to give the new administration time to review the plan's details.