US Senator Jim Risch, a Republican, called himself a “strong proponent” of the Hong Kong Human Rights and Democracy Act and urged its passage.
The bill would re-examine Washington’s special treatment of Hong Kong.
Chinese Foreign Ministry spokesman Geng Shuang attacked Risch, saying he had “turned a blind eye to the blatant beating, smashing and burning perpetrated by Hong Kong demonstrators”.
“I want to reiterate that Hong Kong is China’s Hong Kong. Hong Kong affairs are purely China’s internal affairs and cannot be interfered by any external forces,” he said.
The protests, now in its sixth month, escalated sharply after an officer shot a protester and a man was set on fire on Monday.
For the third day in a row, protesters caused major train service disruptions, blocked streets and rallied in the central business district.
They hunkered down for expected clashes with police at university campuses.
College students from mainland China are fleeing Hong Kong and classes in primary and secondary schools have been suspended.
Geng also criticised the East Turkistan National Awakening Movement, a Uighur-rights organisation, which published hundreds of coordinates of suspected internment camps in China’s far-western Xinjiang region.
Geng called the group’s allegations “groundless”.
“All lies will collapse when faced with facts,” he added.
Experts say China has held one million Muslim members of Xinjiang’s Turkic Uighur ethnic minority and other groups inside mass detention facilities.
Associated Press journalists have witnessed barbed wire, high walls and guard towers at some of the facilities, which Beijing calls vocational training centres.