US Secretary of State Mike Pompeo on Thursday sought to defuse tension over the United Kingdom's decision to allow China's Huawei a role in its communication network but described the Chinese Communist Party as the biggest threat of the current era.

The UK on Tuesday defied the United States by granting Chinese technology firm Huawei a limited role in its 5G network.

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The US, including Pompeo and President Donald Trump, had been lobbying the UK to exclude the firm on security grounds.

Some had predicted a backlash from Trump's administration during Pompeo's two-day visit to Britain.

But while the US Secretary of State showed no softening in his opposition to Huawei, he was eager to downplay the broader impact.

"When you allow the information of your citizens or the national security information of your citizens to transit a network that the Chinese Communist Party has a legal mandate to obtain it creates risk," Pompeo told reporters.

"I am very confident that our two nations will find a way to work together to resolve this difference," Pompeo said, adding that the Five-Eyes intelligence alliance would remain.

Speaking alongside British Secretary of State for Foreign Affairs Dominic Raab, Pompeo said he regarded the Chinese Communist Party as "the central threat of our times" and urged the US and its allies to ensure they have the military and technological power to ensure that this century is governed by Western principles.

The UK's Huawei decision came at a critical juncture as the country prepares to leave the European Union on Friday and begin negotiating a trade deal with the US that it hopes will allow more and freer transatlantic trade.

Pompeo said the "special relationship" - a term used to describe the close Anglo-American alliance - remains in good health and that he wanted to prioritise a post-Brexit trade deal with the UK.

"The previous administration took a view that if the United Kingdom made this decision they'd be at the back of the line - we intend to put the United Kingdom at the front of the line," Pompeo told the Policy Exchange think-tank event.