United States President Donald Trump has criticised the United Kingdom’s plan to hand over the Chagos Islands to Mauritius, a day after his administration gave its official approval of the deal.

Trump said on Wednesday that Prime Minister Keir Starmer was “making a big mistake” in the agreement to transfer sovereignty of the archipelago to Mauritius and lease the island of Diego Garcia, which is home to a UK-US military base.

“DO NOT GIVE AWAY DIEGO GARCIA!” Trump wrote in a post on Truth Social, saying the base could be called upon in any future military operation to counter a potential attack from Iran.

“I have been telling Prime Minister Keir Starmer, of the United Kingdom, that Leases are no good when it comes to Countries, and that he is making a big mistake by entering a 100 Year Lease with whoever it is that is ‘claiming’ Right, Title, and Interest to Diego Garcia,” he added.

He warned in a Truth Social post that Starmer was “losing control of this important Island by claims of entities never known of before”, adding: “In our opinion, they are fictitious in nature.”

The Indian Ocean archipelago was administered as part of Mauritius when the territories were under French control from 1715 to 1810. The UK, which took control of both groups of islands in the early 19th century, detached the Chagos Islands from Mauritius before granting the latter independence in 1968.

The UK then forcibly displaced the residents of the islands to establish the Diego Garcia base.

Mauritius won its legal battle for sovereignty over the islands in 2019, and the International Court of Justice (ICJ) urged the UK to cede control. This was followed by a UN resolution giving the UK six months to hand the islands back.

The UK will maintain a 99-year lease of Diego Garcia with an option to extend, which will cost about 100 million pounds ($135m) a year.

A spokesperson for the UK’s Foreign, Commonwealth and Development Office said on Wednesday that the deal was “crucial to the security of the UK and our key allies, and to keeping the British people safe”.

“The agreement we have reached is the only way to guarantee the long-term future of this vital military base,” the spokesperson said.

Trump’s comments mark the latest in the UK-US diplomatic rollercoaster over the deal.

The UK has said it had no choice but to make a deal after international court decisions threatened its ability to maintain the base under previous arrangements.

Washington last year gave its blessing to the agreement, but in January, Trump described it as an act of “great stupidity”. Earlier in February, he then said he understood the deal was the best Starmer could make, but added he would retain the right to “militarily secure” the base if needed.

On Tuesday, the US Department of State issued a statement which stated its backing for the deal.

“The United States supports the decision of the United Kingdom to proceed with its agreement with Mauritius concerning the Chagos archipelago,” the statement said, announcing talks between the US and Mauritius next week.

In his Truth Social post on Wednesday, the president went on to warn that “it may be necessary for the United States to use Diego Garcia, and the Airfield located in Fairford in order to eradicate a potential attack” from Iran, should it decide against making a deal on its nuclear programme with the US.

Describing the lease as tenuous, he said that the UK must “remain strong in the face of Wokeism, and other problems put before them”.

Diego Garcia serves as a key military base in the Indian Ocean for the US and UK.

Recent operations launched from Diego Garcia include attacks against the Houthis in Yemen in 2024 and 2025 and attacks against the Taliban and al-Qaeda in Afghanistan in 2001.

Up to 2,000 Chagossians were forcibly removed from the archipelago in the 1960s and 1970s and resettled mainly in Mauritius and the UK.

The deal has been criticised by some Chagossians who accuse Mauritius of decades of neglect, an allegation Mauritius denies.