Ministers are increasingly concerned President Donald Trump could cancel the deal to cede sovereignty of the Chagos Islands to Mauritius.
The President had previously derided the act as "stupid" and an "act of total weakness".
In a phone call between Sir Keir Starmer and President Trump, the Prime Minister chose not to mention the treaty, leading to concerns among ministers that the US leader does not understand the deal, reports The Times.
President Trump's British envoy Mark Burnett, initially briefed the President on its contents more than a year ago but diplomatic sources said more senior members of the administration had begun to assert themselves.
This includes Treasury Secretary Scott Bessent and US Ambassador in London Warren Stephens, who are among those who have been lobbied by Reform leader Nigel Farage or senior Conservatives.
Senior Conservatives have suggested their plan is to delay the legislation in the Lords for so long that it fails to pass before the end of the parliamentary session in May.
When pressed on if the deal was dead without American backing, a Downing Street spokesman said: "As the public would rightly expect, we’ve negotiated robust security provisions to protect the UK and the base for decades to come."
FOLLOW BELOW FOR LIVE UPDATES THROUGHOUT THE DAY…
Greeen Party peer calls for BOYCOTT of World Cup over ICE shooting
A Green Party peer has called on British football fans to boycott the World Cup in the US later this year.
Baroness Jenny Jones said: "The horrific shooting of innocent people by Immigration and Customs Enforcement (ICE) raises big concerns about the security of people from this country visiting the USA, especially if they are victims of racial profiling by ICE agents.
"President Trump and his administration have lied on behalf of ICE and given them backing for acting illegally and killing people who they then labels as “domestic terrorists”.
"As someone who was on the Met Police’s domestic extremism database for several years, along with thousands of others, that does not seem like a safe country to visit."
WATCH: Shadow Chancellor of the Duchy of Lancaster Alex Burghart on Labour’s announcement to cut business rates for hospitality jobs by 15 per cent
Keir Starmer says Labour is the only party that can beat Reform in key by-election
Sir Keir Starmer has insisted Labour is the only party that can beat Reform UK in the Gorton and Denton by-election.
Since the resignation of former MP Andrew Gwynne last week, speculation has mounted that Reform could win the seat Labour retained with 51 per cent of the vote in 2024.
The Greens, meanwhile, have sought to portray themselves as the main option for voters wanting to stop Reform as leader Zack Polanski seeks to supplant Labour.
But ahead of his visit to Beijing, Sir Keir told reporters that Labour remained the best way to stop Nigel Farage’s party gaining another MP.
He said: "There’s only one party that can stop Reform and that’s the Labour Party.
"We can already see what the by-election’s going to be about, which is Labour values, which are about delivering, focusing on the cost of living, with a strong record in that constituency of what we’ve already done, versus Reform."
The only two parties who have announced their candidates for the by election so far are Reform UK (Matthew Goodwin) and The Workers Party (Shahbaz Sarwar).
WATCH: Former Political Advisor Oscar Reddrop gives his take on why the Government is giving hospitality businesses a 15% cut to their rates
Senior Tory slams Keir Starmer's Beijing trip
Shadow Duchy of Lancaster Alex Burghart slammed the trip
|GB NEWS
A senior Conservative has said the Government is "not taking the security risk seriously" ahead of Sir Keir Starmer's visit to Beijing.
Shadow Duchy of Lancaster Alex Burghart told GB News: "I think the thing is I don't really know what we're supposed to be getting out of it.
"I know there's a lot of talk about how this will improve trade but its coming off revelations the Chinese government was hacking phones of people who worked in Downing Street.
"Whilst there's some economic opportunity coming from Beijing there's a very large amount of security risk and I don't know if the Government is taking that seriously."
Most deprived areas in UK to get worse by end of Parliament
Britain's most deprived neighbourhoods will have higher crime rates and worse unemployment by the end of the current session of parliament, according to a report written at the request of Downing Street.
The forecasts from the Independent Commission on Neighbourhoods (Icon) show crime rates and unemployment will rise until the next election in England’s 613 most deprived neighbourhoods, despite Labour's promises to invest in local communities.
The report’s authors warn the extra money ministers have pumped in is not enough to counteract longer-term trends such as the increase in antisocial behaviour and the problems facing the retail and hospitality sectors, reports The Guardian.
Keir Starmer accused of unleashing witch hunt against Iraq veterans: 'He insisted on doing it for free!'
Sir Keir Starmer has come under fire
|GETTY
Sir Keir Starmer acted for interveners on a controversial human rights case that ultimately paved the way for hundreds of British soldiers to face allegations of war crimes in Iraq, reports suggest.
Court documents show the Prime Minister worked on the case pro bono alongside Lord Hermer, the Attorney General, representing interveners, including the Law Society of England and Wales.
The case was brought on behalf of Iraqi families who claimed their relatives were unlawfully killed by Britain’s armed forces following the 2003 invasion.
Here's what's happening today in Westminster
Good morning from all of us on the GB News Politics team, here's what's driving the day today in Westminster and beyond.
Our very own Political Editor Chris Hope is currently en route to Beijing alongside the Prime Minister. Friends of GB News can read up why he's headed to China here.
Meanwhile, back in Westminster, it's Deputy Prime Minister's Questions as David Lammy is up to the dispatch box. The Conservatives have not yet confirmed who they'll be putting up to face him.
Angela Rayner has reportedly urged Labour’s leadership to "do better" at a private fundraising dinner as she teased a return to frontline politics ahead of the crucial by-election in Manchester. Our reporter Dan McDonald has the story here.
North of the border, the Conservatives are looking to defend a seat in Scotland after the jailing of a local councillor triggered a by-election. Ben McCaffrey has done a deep dive into the Bearsden South ward in East Dunbartonshire here.
Landlords across the country are continuing their plans to ban Labour MPs from their pubs as "the threshold has not been met" over plans to for pubs and music venues to get 15 per cent off their business rates bills from April.
We'll be hearing today from Andy Lennox, the Dorset landlord who started the ban, says rates reform was only one part of their demands and it was for the whole sector, not just pubs.
He says they stand in solidarity with wider Hospitality who have been excluded and thus will not be lifting the #NoLabourMP ban. Mr Lennox says, “the industry needs meaningful change, today’s announcement was not it."
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