LONDON (AP) — The British government on Tuesday defended its decision to hand sovereignty the Chagos Islands to Mauritius after U.S. President Donald Trump attacked the plan, which his administration had previously supported.

Trump said that relinquishing the remote Indian Ocean archipelago, home to a strategically important American naval and bomber base, was an act of stupidity that shows why he needs to take over Greenland.

“Shockingly, our ‘brilliant’ NATO Ally, the United Kingdom, is currently planning to give away the Island of Diego Garcia, the site of a vital U.S. Military Base, to Mauritius, and to do so FOR NO REASON WHATSOEVER,” he said in a post on his social media platform Truth Social. “There is no doubt that China and Russia have noticed this act of total weakness.”

“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,” he added.

The United Kingdom and Mauritius signed a deal in May to give Mauritius sovereignty over the islands, though the U.K. will lease back Diego Garcia where the U.S. base is located, for at least 99 years.

The U.S. government welcomed the agreement at the time, saying it “secures the long-term, stable, and effective operation of the joint U.S.-U.K. military facility at Diego Garcia.”

U.K. Cabinet Minister Darren Jones said Tuesday that the agreement would “secure that military base for the next 100 years.”

British opposition parties have slammed the deal as a risk to U.K. national security that will give China more access to the region.

The U.S. has described the Diego Garcia base, which is home to about 2,500 mostly American personnel, as “an all but indispensable platform” for security operations in the Middle East, South Asia and East Africa.