The US Senate on Thursday unanimously approved a bill that would lay out sanctions on Chinese officials who undermine Hong Kong's autonomy as Beijing pushes forward with a controversial security law.

The House of Representatives still needs to pass the bill, which would allow sanctions in the United States against Chinese officials and the Hong Kong police as well as banks that do business with them.

The vote comes as China presses forward with a security law that would enforce punishment over subversion and other perceived threats in Hong Kong, which saw massive protests last year in support of maintaining the financial hub's freedoms.

"They are moving forward in their process to take away the liberties of the people of Hong Kong. So time is of the essence," said Senator Chris Van Hollen, a Democrat who helped lead the charge on the bipartisan bill.

"Passing a Senate resolution as the consequence to their action is hardly going to be taken seriously in Beijing," he said on the Senate floor.

"And that's why it's important to actually do something that shows that the government of China will pay a price if it continues down this path to extinguish those freedoms of the people in Hong Kong."

The bill is likely to be easily passed in the Democratic-led House of Representatives, which has repeatedly taken China to task on rights issues.

President Donald Trump's administration has already declared that it no longer considers Hong Kong autonomous under US law.

But it has so far outlined comparatively symbolic measures as repercussions and has not questioned the overall trading relationship with the city.

China promised to preserve a separate system for Hong Kong before taking back the territory from Britain in 1997.