President Donald Trump sharply criticized Britain’s agreement to cede sovereignty of the Chagos Islands to Mauritius, insisting the UK retain control of Diego Garcia. The Indian Ocean island hosts a key joint U.S.-UK military base used for operations across the Middle East and Asia. Trump warned that surrendering the territory would damage ties with a ‘Great Ally.’

In his Truth Social post, Trump dismissed long-term leases as unreliable. He highlighted Diego Garcia’s position amid rising tensions with Iran over its nuclear program. Trump has threatened military action against Tehran, which denies the allegations. ‘This base could be CRITICAL if we have to use force,’ he wrote.

The UK struck the deal last month with Mauritius, agreeing to transfer sovereignty of the British Indian Ocean Territory while securing a 99-year lease on Diego Garcia. Prime Minister Keir Starmer defended the pact as vital to the base’s future. Legal rulings, including from the International Court of Justice, have challenged Britain’s claim over the islands, roughly 1,250 miles northeast of Mauritius.

Trump’s remarks clash with the U.S. State Department’s stance. Officials there endorsed the agreement on Tuesday, calling it the best way to protect base access. The president has flip-flopped before, once labeling the deal ‘great stupidity’ and later the ‘best’ option.

Britain has controlled the Chagos Islands since 1814. In the 1960s, it cleared the atolls for the U.S. base, displacing about 1,500 islanders known as Chagossians. Many now live in Mauritius, Seychelles or the UK, and continue to demand the right of return.

Mauritius has pressed its claim since independence in 1968, arguing Britain illegally detached the islands. The Foreign Office stressed the agreement bolsters security for the UK and allies. ‘This secures the base for generations,’ a spokesperson said.

Trump’s intervention drew quick reactions in Westminster. Conservative MP Priti Patel dubbed it ‘an utter humiliation’ for Starmer’s government. Liberal Democrat leader Ed Davey said it exposed Britain’s over-reliance on a Trump-led Washington. Reform UK’s Nigel Farage cheered the criticism and called for scrapping the deal outright.

U.S.-Mauritius talks are set for next week. Officials will discuss base operations as the dispute heats up. Diego Garcia supports B-2 bomber missions, surveillance flights and prepositioned supplies. Its runways and lagoons anchor U.S. power projection in the region.

Starmer’s team shows no sign of backing down. The prime minister told Parliament the pact ends years of uncertainty. Critics, including Chagossian groups, argue it ignores islanders’ rights while prioritizing military needs.

Trump’s post arrived hours after the State Department’s nod. It highlights rifts in his administration’s foreign policy. Advisors have pushed the deal to lock in access amid China’s growing Indian Ocean presence.