Donald Trump has signed a bill into law that backs pro-democracy protesters in Hong Kong, despite angry objections from Beijing.
The Human Rights and Democracy Act, one of two laws the president signed in relation to the demonstrators, aims to ensure Hong Kong has significant autonomy from the rest of China.
It requires the State Department to certify, at least annually, that Hong Kong retains enough autonomy to justify favourable US trading terms that have helped it maintain its position as a world financial centre.
The law also threatens sanctions for human rights violations.
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Congress passed a second bill, which President Trump also signed, banning the export to the Hong Kong police of crowd-control munitions, such as tear gas, pepper spray, rubber bullets and stun guns.
"I signed these bills out of respect for President Xi (Jinping), 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," Mr Trump said in a statement.
The legislation was approved unanimously by the US Senate and by all but one lawmaker in the House of Representatives last week.
It comes as Mr Trump is seeking a deal with China, in order to end a damaging trade war between the countries.
China has denounced the legislation as gross interference in its affairs and a violation of international law. After the Senate passed the legislation, Beijing vowed counter-measures to safeguard its sovereignty and security.
At the heart of matter is Beijing's promise to allow Hong Kong a "high degree of autonomy" for 50 years when it regained sovereignty over the city in 1997, a pledge that has formed the basis of the territory's special status under US law.
Protesters say freedoms have been steadily eroded.
