The U.S. Senate unanimously passed a bill Tuesday aimed at supporting protesters in Hong Kong and warning China against a violent suppression of the demonstrations — drawing a rebuke from authorities in Beijing.

China reiterated Wednesday a threat to impose unspecified retaliation if the bill became law and urged the U.S. to stop meddling in Hong Kong affairs. Separately, the city's government expressed "extreme regret" over the bill, saying it would negatively impact relations between Hong Kong and the U.S.

The Senate measure would require the State Department to certify annually whether Hong Kong remains sufficiently autonomous from Beijing to justify special trade privileges, as well as protect U.S. citizens from rendition to China through measures including sanctions on mainland officials.