China has accused the United States of interfering in its internal affairs after the US Senate passed a Hong Kong rights Bill.
Beijing warned it would take countermeasures if the Bill is signed into law.
China's Vice-Minister of Foreign Affairs Ma Zhaoxu yesterday summoned a senior US diplomat over the issue amid a chorus of condemnation by various Chinese organs.
The US Senate unanimously passed the Bill in support of pro-democracy protests in Hong Kong on Tuesday evening. It allows for diplomatic and economic sanctions if Washington deems Beijing to have crossed the line in eroding Hong Kong's autonomy.
Chinese Foreign Ministry spokesman Geng Shuang unleashed a torrent of criticism at the Bill when he condemned it during a daily briefing yesterday, saying it "disregards the facts, confuses right and wrong, violates the truth, plays up double standards, interferes in Hong Kong affairs and China's internal affairs, and seriously violates the basic norms of international law and international relations".
"We are warning the US to recognise what the situation is and rein in their horses before they head off the precipice," he added.
"The US should immediately take measures to prevent the Bill from becoming law... otherwise, they would ignite a fire that would burn themselves and must bear the bitter consequences."
Beijing would take strong countermeasures to safeguard its interests and national sovereignty and security if the US persisted, added Mr Geng, without elaborating.
The Hong Kong Human Rights and Democracy Act, a version of which was unanimously passed by the US House of Representatives last month, has presented President Donald Trump with a dilemma: choose between drawing Beijing's wrath by signing it into law and risking blowback from a remarkably bipartisan Congress by vetoing it.
Various Chinese organs - including the top legislature, the Hong Kong and Macau Affairs Office of China's Cabinet, and the Hong Kong Liaison Office, the central government's top authority in the territory - also denounced the US move in public statements yesterday.
Hong Kong's government expressed "extreme regret", saying in a statement that the Bill was "unnecessary and unwarranted", and would negatively impact relations between Hong Kong and the US.
A spokesman said: "Any unilateral change of US economic and trade policy towards Hong Kong will create negative impact on the relations between the two sides as well as the US' own interests."
The passage of the law comes amid escalating clashes between protesters and police in Hong Kong, including an ongoing stand-off at The Hong Kong Polytechnic University, where about 100 protesters have been holed up for days and more than 1,100 others arrested.
The US Senate Bill received strong bipartisan support and was co-sponsored by half the Senate at the time of its signing. Its sponsors included Senate Majority Leader Mitch McConnell, who on Monday publicly encouraged Mr Trump "not to shy away from speaking out on Hong Kong".
It will require the US Secretary of State to certify, at least annually for the next seven years, whether Hong Kong remains sufficiently autonomous, and is meant to encourage Beijing to respect Hong Kong's autonomy or risk the city losing its special status under American law.
Republican Senator Marco Rubio, one of several senators who introduced the Bill in June, said: "What China is really pushing for in Hong Kong is moving from one country, two systems to one country, one system - the Chinese system."
Mr Hu Xijin, editor of China's nationalist Global Times, accused the US of turning Hong Kong into a focal point of China-US competition.
"It's all the people in Hong Kong, including foreigners and foreign companies, that suffer. The mainland only feels limited pain. Beijing has no reason to back off on (the) issue of sovereignty, and let HK be at (the) US' disposal," he said in a tweet yesterday.