US President Donald Trump signed a law supporting pro-democracy protesters in Hong Kong.
The decision was condemned by Hong Kong and Chinese authorities.
"I signed the Hong Kong Human Rights and Democracy Act," the US president announced in a statement, AFP reports.
"The Hong Kong government expressed its deep regret over Trump's decision and accused Washington of "interference" in Hong Kong's internal affairs."
Beijing said it had summoned the US ambassador to China for a chat, urging Washington not to enforce the law.
Chinese Vice Foreign Minister Le Yuceng told US Ambassador Terry Branstad that China "strongly opposes" the law.
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"China urges the US to correct the mistake so as not to further damage Sino-US relations and cooperation," the Chinese Foreign Ministry said in a statement.
Protests in Hong Kong have been going on since early June.
They were initially organized to oppose a bill that would have allowed suspects to be extradited to Beijing, but quickly turned into a battle for democratic rights and the preservation of civil liberties guaranteed to Hong Kong in 1997, when Great Britain returned the territory to China/Rel.
