U.K. agrees to hand the Chagos Islands to Mauritius in a deal it says protects a key U.S. base

People demonstrate outside the High Court in London, Thursday, May 22, 2025. (AP Photo/Thomas Krych)

LONDON — Britain signed an agreement Thursday to hand sovereignty over the contested Chagos Islands to Mauritius, a move the government says ensures the future of a U.S.-U.K. military base that is vital to British security.

The Indian Ocean archipelago is home to a strategically important naval and bomber base on the largest of the islands, Diego Garcia.

Under the agreement, the U.K. will pay Mauritius an average of 101 million pounds (US$136 million) a year to lease back the base for at least 99 years.

Prime Minister Keir Starmer said that base, operated by U.S. forces, is crucial for British counterterrorism and intelligence and is “right at the foundation of our safety and security at home.”

“By agreeing to this deal now on our terms, we’re securing strong protections, including from malign influence, that will allow the base to operate well into the next century, helping to keep us safe for generations to come,” Starmer told reporters at a U.K. military headquarters in Northwood, near London.

Critics of the deal, which must be approved by Parliament, argue that giving up the islands, which have been British territory for two centuries, puts them at risk of interference by foreign powers such as Russia or China.

Conservative defence spokesman James Cartlidge called the deal a “total, abject surrender of our territory and a fundamental betrayal of the U.K. national interest.”

The agreement was struck in the face of opposition from some of the islands’ original residents, who were expelled decades ago to make way for the base.

The agreement was due to be signed by Starmer and Mauritian leader Navin Ramgoolam at a virtual ceremony on Thursday morning. But signing was delayed for several hours after a U.K. judge imposed a last-minute injunction blocking the transfer at the behest of two Chagossian campaigners. The injunction was later lifted by another judge.

Displaced islanders have fought unsuccessfully in U.K. courts for years for the right to go home. Chagos-born Bernadette Dugasse and Bertrice Pompe, who brought the latest legal challenge, fear it will become even harder to return to their birthplace once Mauritius takes control.

The deal establishes a trust fund to benefit the Chagossians and says “Mauritius is free to implement a program of resettlement” on the islands, other than Diego Garcia. But it does not require the residents to be resettled.

Pompe said it was “a very sad day,“ but vowed to continue fighting.

“The rights we are asking for now, we have been fighting for for 60 years,” she said outside the High Court. ”Mauritius is not going to give that to us.”

One of the last remnants of the British Empire, the Chagos Islands have been under U.K. control since 1814. Britain split the islands away from Mauritius, a former British colony, in 1965, three years before Mauritius gained independence.

Britain evicted as many as 2,000 people from the islands in the 1960s and 1970s so the U.S. military could build the Diego Garcia base, which has supported U.S. operations from Vietnam to Iraq and Afghanistan. It has facilities to accommodate nuclear submarines, aircraft carriers and large airplanes, and plays a key role in U.S. intelligence-gathering.

Mauritius has long contested Britain’s claim to the archipelago, and the United Nations and its top court have urged Britain to return the Chagos to Mauritius, around 2,100 kilometres (1,250 miles) southwest of the islands.

In a non-binding 2019 opinion, the International Court of Justice ruled that the U.K. had unlawfully carved up Mauritius when it agreed to end colonial rule in the late 1960s.

Starmer said that “we had to act now because the base was under threat.”

He said Mauritius is likely to have taken Britain to court within weeks and the U.K. had no “realistic prospect of success.”

Britain’s defence ministry said the deal includes strong protections, including a 24-mile (39 kilometre) exclusion zone around Diego Garcia, a U.K. veto over development on the wider islands and a ban on foreign security forces on the islands.

Negotiations on handing the islands to Mauritius began in 2022 under the previous Conservative government and resumed after Starmer’s Labour Party was elected in July.

A draft agreement was struck in October, but was delayed by a change of government in Mauritius and quarrels over how much the U.K. should pay to lease the base.

Britain also paused to consult President Donald Trump’s administration after the change of government in Washington.

Secretary of State Marco Rubio welcomed the agreement, saying it “secures the long-term, stable, and effective operation” of the Diego Garcia base, ”a critical asset for regional and global security. “

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Associated Press writer Matthew Lee in Washington contributed.

Jill Lawless, The Associated Press