The new legislation requires the State Department to ensure that Hong Kong retains sufficient autonomy to enjoy favorable US trading terms that have helped the city to maintain its position as a major financial hub.
US President Donald Trump on Wednesday signed a congressional bill backing Hong Kong protesters into law, drawing stiff threats from China.
The legislation, which had overwhelming support from Congress, requires the State Department to certify at least annually that Hong Kong's autonomy is not compromised. It also allows the US to impose sanctions for human rights abuses.
Read more: Hong Kong crisis: What you need to know
Congress also passed a second bill — which President Trump also signed — that banned the export of crowd-control munitions, such as teargas, pepper spray, rubber bullets and stun guns, to the Hong Kong security forces.
Trump, who is eager to strike a new trade deal with Beijing, was reluctant to sign the bill but faced veto proof support in Congress.
"I signed these bills out of respect for President Xi, China, and the people of Hong Kong. They are being enacted in the hope that Leaders and Representatives of China and Hong Kong will be able to amicably settle their differences leading to long term peace and prosperity for all," Trump said in statement.
China's foreign ministry said Thursday that the legislation was a serious interference in Chinese affairs and a "blatant hegemonic act."
"We advise the United States not to act arbitrarily, or China will resolutely counteract it, and all consequences arising therefrom must be borne by the United States," the ministry said.
US Ambassador Terry Branstad was later summoned to the Chinese Foreign Ministry.
Hong Kong's government said the bill sent a wrong signal to sometimes violent protesters and "clearly interfered" in the city's internal affairs.
China urged Trump last week to veto the two bills, renewing a threat to take unspecified retaliatory steps if the bills were signed into law.
"This bill sends the wrong signal to those violent criminals and its substance seeks to throw Hong Kong into chaos or even to destroy Hong Kong outright,'' Foreign Minister Wang Yi said on November 21 during a visit from US Defense Secretary William Cohen.
"If the US continues to make the wrong moves, China will be taking strong countermeasures for sure," Foreign Ministry spokesman Geng Shuang said.
Hong Kong's turmoil nears six months of increasingly violent pro-democracy protests triggered by a now-shelved bill that would have allowed extraditions to China.
The protests broadened into a movement calling for democratic reforms, and has been driven by concerns that China is encroaching on freedoms in Hong Kong that are not enjoyed on the mainland.
Police enter campus
On Thursday, Hong Kong police entered a university campus at the end of a nearly two-week siege that saw some of the worst clashes between protesters and security forces.
According to city officials, a team of about 100 plain-clothed police officers entered the Polytechnic University to collect evidence, removing dangerous items such as petrol bombs that remain scattered around the campus.
shs/se (Reuters, AP, AFP)