UK Prime Minister Boris Johnson gave the green light to Huawei to develop the UK's 5G network.

The UK government defied the US to give the Chinese company a role in improving the UK's digital infrastructure.

The Trump administration has urged the UK government not to do a deal with Huawei, saying it would give Chinese intelligence services a back door into Britain.

The UK government said it would limit Huawei's role and restrict its access to "sensitive" parts of the network.

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UK Prime Minister Boris Johnson defied the Trump administration and granted permission to the Chinese telecoms company Huawei to help develop Britain's 5G network.

The UK government said in a written statement on Tuesday that it would give Huawei a major role in building the country's 5G network, despite warnings about potential threats to security.

But the UK's Department for Culture, Media, and Sport said Huawei would be excluded from the network's "core" functions, operating just 35% of the overall network.

The company will also be excluded from operating "sensitive" parts of the UK's communications network, "such as nuclear sites and military bases."

"We want world-class connectivity as soon as possible but this must not be at the expense of our national security," Digital Secretary Baroness Morgan said. "High risk vendors never have been and never will be in our most sensitive networks."

In a statement, Huawei welcomed Downing Street's "evidence-based" decision to allow the firm to continue its rollout of the 5G network.

"Huawei is reassured by the UK government's confirmation that we can continue working with our customers to keep the 5G roll-out on track," said Victor Zhang, Huawei's vice president.

"This evidence-based decision will result in a more advanced, more secure and more cost-effective telecoms infrastructure that is fit for the future."

The US strongly opposed the UK allowing Huawei to develop its infrastructure, saying that doing so would give Chinese state intelligence services a back door into Britain and put UK-US intelligence sharing at risk.

US Secretary of State Mike Pompeo, who is due to visit London this week, warned Johnson on Sunday that he faced a "momentous" decision on whether to freeze the telecoms giant out of new UK infrastructure.

Pompeo endorsed a tweet from Tom Tugendhat, one of several MPs in Johnson's Conservative Party who have expressed concern about Huawei, saying that allowing Huawei into such a critical part of infrastructure could have a "real cost" and undermine the UK's sovereignty.

However, the prime minister has opted to go ahead with plans to let the Chinese company develop Britain's 5G network as part of his agenda of "levelling up" regions across the country through improved infrastructure.

The UK government has been advised by security services that a deal with Huawei would not put intelligence at risk.

The government is expected to make a House of Commons statement on the decision later on Tuesday.

Trump's Huawei threats 'irritated' Johnson

Johnson and Trump. Dan Kitwood/Getty Images)

The Times reported on Monday that the repeated threats from Trump and his allies "irritated" Johnson's administration, with Johnson calling on critics to put forward an alternative for developing UK 5G.

Asked earlier this month whether he would allow the Huawei deal to go ahead, the prime minister told the BBC that "the British public deserves access to the best possible technology."

He added, "If people oppose one brand or another, they have to tell us, what's the alternative?"

This disagreement between London and Washington comes weeks before the two sides are set to sit down to negotiate a post-Brexit free-trade deal.

US Rep. Mike Gallagher told the BBC on Monday that letting Huawei develop its 5G network would thwart the UK's chance of a comprehensive trade agreement with the US.

"Regardless of who wins the White House in 2020, I think it would make it very difficult — if not impossible — to reach that gold-standard trade agreement which we all want," he said.