LONDON — Secretary of State Mike Pompeo declared the Chinese Communist Party “the central threat of our times” on Thursday, even as he sought to talk up the prospects of a United States trade deal with Britain, which rebuffed American pressure to ban a Chinese company from future telecommunications infrastructure.

The scathing criticism of the Chinese government was the strongest language Mr. Pompeo has used as the Trump administration seeks to convince American allies of the risks posed by using equipment from Huawei, a Chinese technology giant.

At the same time, Mr. Pompeo sought to reassure British officials that even though the two countries saw the issue differently, it would not undermine the strong bond between them.

Mr. Pompeo’s reassurances come at a delicate moment for the British government as it begins the process of forging new stand-alone trade deals after it formally leaves the European Union on Friday.