The extension, just weeks before the program was due to run out, is likely to add to tensions between Beijing and Washington as the incoming administration of Donald Trump vowed to confront a "dangerous" China and deter any invasion of Taiwan.

It is the second time Biden has extended the program. He also did so for two years in 2022.

"Offering safe haven for Hong Kong residents who have been deprived of their guaranteed freedoms in Hong Kong furthers United States interests in the region," Biden said in a presidential memorandum.

"The United States supports the human rights and fundamental freedoms of the residents of Hong Kong. The People's Republic of China (PRC) has continued to significantly erode those rights and freedoms," he said.

Biden laid out what he described as the Chinese communist government's "assault on Hong Kong's autonomy" and undermining of remaining democratic institutions.

This includes at least 200 arrests of politicians and activists on politically motivated national security charges such as subversion since 2020, when a draconian national security law came into force in Hong Kong, and the sentencing last year of 45 pro-democracy advocates to prison, he said.

"There are compelling foreign policy reasons to extend" the visa clemency program, known as Deferred Enforced Departure, Biden said.

The previous program was due to expire on February 5.

The State Department added that on December 24, Hong Kong authorities issued arrest warrants and bounties targeting six overseas democracy activists and cancelled passports for seven other activists, including some based in the United States.

"These acts of transnational repression are a threat to US sovereignty and national security and show blatant disregard for democracy and human rights," spokesman Matthew Miller said in a statement.