Donald Trump has told Britain's Prime Minister Sir Keir Starmer "to remain strong in the face of wokeism" and not give away the Chagos Islands.
The US president believes the UK is making a "big mistake" in its decision to transfer sovereignty of the islands to Mauritius.
Under an agreement made in 2025, Britain will cede the archipelago to Mauritius but retain control of the strategically important Diego Garcia military base under a 99-year lease.
"DO NOT GIVE AWAY DIEGO GARCIA!" Trump wrote in all caps on his social media platform, Truth Social.
The Chagos Islands sit in the Indian Ocean, about 500 kilometres from the Maldives, its nearest neighbour.
The archipelago comprises of 60 islands and is home to just under 5,000 people.
So why does the US president care so much about them? Military flexibility.
'Big mistake'
"Prime Minister Starmer should not lose control, for any reason, of Diego Garcia, by entering a tenuous, at best, 100 Year Lease," Mr Trump said.
The US president added he has spoken with Sir Keir about the Chagos Islands, telling him "leases are no good when it comes to countries".
"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 said.
In response to Mr Trump, a British Foreign Office spokesperson said the deal was "crucial to the security of the UK and our key allies".
"The agreement we have reached is the only way to guarantee the long-term future of this vital military base," the statement added.
Under the agreed terms with Britain and Mauritius, the UK would need to agree in advance to any operations out of Diego Garcia.
A meeting between Britain's Foreign Minister Yvette Cooper and US Secretary of State Marco Rubio took place on Friday in Washington.
The pair discussed the lease agreement, as well as mutual defence and security issues.
The UN Committee on the Elimination of Racial Discrimination has urged Britain and Mauritius not to ratify the agreement.
It said it risks perpetuating historical rights violations.
The deal has been criticised by some Chagossians who accuse Mauritius of decades of neglect, an allegation Mauritius denies.
Trump willing to 'militarily secure' the base
Mr Trump has changed his feelings over the Chagos Islands situation several times since he took office for the second time.
Last year, Washington gave its blessing to the agreement, however, in January, Mr Trump described it as an act of "great stupidity".
Earlier in February, he flipped again, saying he understood the deal was the best the UK could make, before then renewing his criticism this week.
His comments this week highlight yet another ebb in the ongoing Anglo-American diplomatic rollercoaster over the deal.
Britain 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.
When the US president said he thought the deal was the best Sir Keir could do, he added he would retain the right to "militarily secure" the base if needed.
On Tuesday, February 17, the US State Department issued a statement that said it backs the deal made by the UK and Mauritius.
"The United States supports the decision of the United Kingdom to proceed with its agreement with Mauritius concerning the Chagos archipelago," the statement said.
Chagossians protest the deal
Up to 2,000 Chagossians were forcibly removed from the archipelago in the 1960s and 1970s, and resettled mainly in Mauritius and Britain.
Many of those who are still alive want the right to return.
On February 17, four Chagos islanders landed on one of the atolls to establish what they said would be a permanent settlement.
One of those people, Misley Mandarin, said they were living in tents and expected 10 more arrivals next week plus many more in the coming year.
He told Reuters that his father, Michel Mandarin, 74, was with him and had been removed from the island when he was 14.
"I am not in exile anymore. This is my homeland," Mr Mandarin said.
Mauritius Attorney General Gavin Glover said the group had landed illegally.
He said it was a "publicity stunt organised to create a situation of conflict with the British government".
In response, British authorities issued removal orders against four Chagossians who landed on the atoll.
A spokesperson at the British Foreign Office called their arrival an "illegal, unsafe stunt" that would not help the UK government's joint work with Mauritius.
ABC/Wires
