But after speaking with British Prime Minister Keir Starmer, Trump warned in a post on Truth Social that he retains the right to "secure and reinforce" the US presence on Diego Garcia island, which is home to the base, if the British deal comes undone or the American presence is threatened.

Under a deal agreed in May of last year, Britain will hand back the Chagos islands, which include Diego Garcia, to Mauritius but keep the base, jointly run by US and British forces, on a 99-year lease.

Trump initially endorsed this accord but then last month changed his mind.

"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 said on January 20.

On Thursday, Trump said Starmer made "the best deal he could make" on the Chagos Islands, which had been at the center of a decades-long diplomatic battle.

Trump said: "However, if the lease deal, sometime in the future, ever falls apart, or anyone threatens or endangers US operations and forces at our Base, I retain the right to Militarily secure and reinforce the American presence in Diego Garcia."

In their conversation Thursday Starmer and Trump agreed to work "closely" on the implementation of the Chagos Islands agreement, the UK leader's office said.