The Asia-focused British banking giant last week posted its support for the law on Chinese social media platform WeChat with a picture of HSBC's top Asia executive, Peter Wong, signing a petition backing the measure.

"That show of fealty seems to have earned HSBC little respect in Beijing, which continues to use the bank's business in China as political leverage against London," Pompeo said in a statement, calling HSBC's experience "a cautionary tale."

"Beijing's aggressive behaviour shows why countries should avoid economic over-reliance on China and should guard their critical infrastructure from CCP influence," he said, referring to the Chinese Communist Party.

Pompeo renewed his call on all countries to shun Chinese telecom giant Huawei, which Washington says will jeopardise personal security if it is allowed to dominate construction of the fifth-generation internet.

The National People's Congress last month moved ahead with a law that will punish subversion and other offences in Hong Kong, a move some activists say will kill the SAR's promised freedoms.

Pompeo responded by declaring that Hong Kong will no longer be considered autonomous in the eyes of US law.