LONDON — The UK on Tuesday defended its deal to hand the Chagos Islands to Mauritius saying it secured the future of a key US-UK military base on the Indian Ocean archipelago.

The British government said the deal was made precisely for national security reasons. "We acted because the base on Diego Garcia was under threat after court decisions undermined our position and would have prevented it operating as intended in future," a spokesperson said, responding to US President Donald Trump's comments on the deal.

Trump described Britain's deal to cede sovereignty of the Chagos Archipelago as an act of "total weakness" and "great stupidity".

The US president’s comments mark a major change of position for Trump, who previously endorsed the deal when it was signed in May 2025.

“The UK giving away extremely important land is an act of GREAT STUPIDITY, and is another in a very long line of National Security reasons why Greenland has to be acquired,” Trump posted on his Truth Social platform earlier on Tuesday.

The harsh comments follow Trump’s threat to slap tariffs on Britain and other European countries for defending Greenland’s sovereignty from Washington.

The Chagos agreement will see Britain hand the archipelago to its former colony and pay to lease the US-UK military base on Diego Garcia, the largest island, for a century.

“This deal secures the operations of the joint US-UK base on Diego Garcia for generations, with robust provisions for keeping its unique capabilities intact and our adversaries out,” Downing Street said in response to Trump’s criticism.

“It has been publicly welcomed by the US, Australia and all other Five Eyes allies, as well as key international partners including India, Japan and South Korea,” a government spokesperson added.

Washington had last year given its blessing to the deal which gave the Indian Ocean islands to Mauritius but retained UK control of the Diego Garcia base under a 99-year lease.

US Secretary of State Marco Rubio had said in May that Washington “welcomes the historic agreement.”

“The Trump Administration determined that this agreement secures the long-term, stable, and effective operation of the joint US-UK military facility at Diego Garcia,” Rubio said in a statement at the time.

“The treaty has been signed with the Mauritian government. So I can’t reverse the clock on that,” UK cabinet minister Darren Jones told Times Radio.

He added that the deal was in the final stages of going through parliament.

The UK kept control of the Chagos Islands after Mauritius gained independence from Britain in the 1960s.

But it evicted thousands of Chagos islanders, who have since mounted a series of legal claims for compensation in British courts.

In 2019, the International Court of Justice recommended that Britain hand the archipelago to Mauritius after decades of legal battles.

Challenges in international and domestic courts had left the status of the military base “under threat,” according to the UK government.

Opposition politicians in the UK have been critical of the deal, which would see Britain pay Mauritius £101 million ($136 million) annually for 99 years to lease Diego Garcia.

The net cost over the length of the lease would be around £3.4 billion if inflation was factored in, according to the government.

Kemi Badenoch, leader of the opposition Conservative party, said: “Unfortunately on this issue President Trump is right.”

“Thank goodness Trump has vetoed the surrender of the Chagos islands,” said Nigel Farage, the populist leader of the hard-right Reform UK party.

But Ed Davey, leader of the centrist Liberal Democrat party, said Labour Prime Minister Keir Starmer should begin to stand up to the US leader.

“This shows Starmer’s approach to Trump has failed. The Chagos Deal was sold as proof the government could work with him. Now it’s falling apart. It’s time for the government to stand up to Trump; appeasing a bully never works.”

Trump's attack heaps new strain on relations with Prime Minister Keir Starmer, who this week spoke out against his ambition to take over Greenland by any means to counter the encroaching presence of rivals China and Russia.

Starmer had built a solid relationship with Trump, becoming the first leader to secure a deal to lower some tariffs, but that has been shaken with disagreement over Greenland and now the Chagos islands furor. — Agencies