President Donald Trump will reportedly tell Theresa May next week that the United States will stop sharing intelligence with the UK unless London scraps its plans to allow Huawei to build a 5G mobile phone network.
The Financial Times said Trump planned to deliver the bad news in person during his three-day visit to the UK, which begins on Monday, 3 June.
US Secretary of State Mike Pompeo warned UK Foreign Secretary Jeremy Hunt earlier this month that intelligence sharing between the CIA, MI5, MI6 and GCHQ may be at risk if Britain goes ahead with the link up with Huawei, which the Pentagon accuses of being a trojan horse for the Chinese military, something Beijing denies.
A White House source told the FT: "The president is preparing to repeat the message that Chinese involvement in 5G could pose significant challenges for US-UK intelligence co-operation."
5G is set to bring faster internet speeds and on Thursday, 30 May, EE launched its new 5G network, which is expected to be followed soon by Vodafone.
At a meeting on 23 April Britain's National Security Council has reportedly agreed to let Huawei provide "non-core" technology, like antennas, to companies like EE and Vodafone but not core technology like software.
UK Defence Secretary Gavin Williamson was sacked by Theresa May on 1 May after she accused him of having leaked information from the National Security Council to the media in an attempt to embarrass the government and block the Huawei link.
Williamson strongly denied the allegation but was replaced by Penny Mordaunt.
But the British government has reportedly refused to allow Huawei to provide "core" technology like software
Huawei has been under pressure from the Trump administration, which claims its equipment could be used for espionage by the Chinese government.
Huawei is also facing charges from the US Justice Department after being accused of stealing trade secrets and flouting sanctions on Iran.
May will step down on 7 June and become a caretaker prime minister until the Conservative Party chooses a new leader.
The front-runner, Boris Johnson, was born in New York and has been called a "friend" by President Trump. Johnson is expected to boost Anglo-American relations, at the expense of Europe.