President Donald Trump has signed two separate bills backing pro-democracy demonstrators in Hong Kong, despite a trade deal in the balance and threats from Beijing.
The House and Senate passed both bills last week nearly unanimously.
One law requires the State Department to certify annually that China allows Hong Kong enough autonomy to guarantee its favorable trading status. It threatens sanctions on Chinese officials who do not.
The second bans the export of tear gas, pepper spray, rubber bullets and other non-lethal ammunition to Hong Kong police.
On Thursday, China's Vice Foreign Minister Le Yucheng summoned U.S. Ambassador Terry Branstad to demand that the United States immediately stop interfering in its internal affairs and stop causing further damage to bilateral relations, its foreign ministry said.
Branstad was summoned a day after Trump signed the legislation, Reuters reported.
But Trump, appearing on Fox News late Tuesday, called Chinese President Xi Jinping "a friend of mine. He's an incredible guy."
"I signed these bills out of respect for President Xi, China and the people of Hong Kong," Trump said in a later statement. "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 had twice called the large street protests in Hong Kong "riots" — a word the protesters say plays into the hands of Chinese authorities.
But Trump took credit for thwarting Beijing's threat to send in 1 million soldiers to put down the marches by saying such a move would have a "tremendous negative impact" on trade talks.
Protests erupted in Hong Kong in June over the local government's plans to allow some criminal suspects to be extradited to the Chinese mainland.
Hong Kong withdrew the bill in September, but the street protests have continued, with the demonstrators fearing Beijing is preparing to water down Hong Kong's democracy and autonomy, nearly 30 years before the ex-British colony's "special status" expires
Some of the protests have turned violent, with marchers throwing gasoline bombs at police, who have responded with live gunfire.