Donald Trump has formally signed off Sir Keir Starmer’s deal to hand the Chagos islands over to Mauritius, No 10 has said.
The agreement is now being “finalised” between the UK and Mauritius.
A Downing Street spokesperson said: “We are now working with the Mauritian government to finalise the deal and sign the treaty.”
A source added: “It's now between us and the Mauritian government to finalise the deal following the discussions with us. We have had the discussions with the US and we are now finalising with the Mauritians.”
The revelation comes after the US president strongly indicated that he would back the deal when he met with Sir Keir in the White House in February, despite early indications he was sceptical of the deal.
At the time Mr Trump said: “I have a feeling it is going to work out very well. I think we will be inclined to go along with your country.”
Critics have warned the deal, which reports suggest could cost as much as £18bn, unnecessarily leases back a strategically vital airbase that the UK already owns.
The plan follows an International Court of Justice (ICJ) ruling that the archipelago belongs to Mauritius, which critics point out is not binding on the UK.
However, UK officials have told the White House that the judgment provided too much legal uncertainty for the crucial airbase and the deal would not cost the US taxpayer anything.
The Indian Ocean islands represent an important part of UK-US security plans because of the strategically crucial Diego Garcia airbase.
As part of the agreement, the UK and US believe they have secured use of the airbase for at least 99 years, but have so far refused to publish how much they will pay to be allowed to use it.
The sign-off will come as a relief to the PM as he braces for difficult news from Mr Trump later this week.
The UK government expects to be hit by tariffs in a move the US president has dubbed “Liberation Day”.
In the wake of the announcement that President Trump had signed off the deal, further concerns were raised about reports that Iran may be contemplating a military strike on the Diego Garcia base , in a point of order in the Commons by Tory shadow defence minister Mark Francois.
He asked ministers to update MPs “regarding an implied military threat to the Chagos Archipelago, or a legal and diplomatic threat to the Chagos Islands, which are, and should remain, fundamentally British."
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