The Hong Kong Human Rights and Democracy Act passed the House of Representatives by 417 to 1 on Wednesday, one day after the Senate unanimously passed the measure.
The bill requires the US president to annually review the favourable trade status that Washington grants to Hong Kong, and threatens to revoke it if the semi-autonomous Chinese territory's freedoms are quashed.
The White House has not threatened to veto the measure and President Donald Trump is expected to sign it, according to a source familiar with the matter.
"We strongly condemn and firmly oppose the passage of relevant Hong Kong-related bills," Chinese foreign ministry spokesperson Geng Shuang said at a regular press briefing.
Geng warned the United States against interfering in Hong Kong and China's internal affairs.
"If the US side is determined to act alone, China will take effective measures to resolutely fight back," he said, without giving more details about what action Beijing might take.
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