U.S. President Donald Trump on Thursday warned against China's possible move to introduce a national security law in Hong Kong following the territory's pro-democracy protests last year that sometimes turned violent.

"If it happens, we'll address that issue very strongly," Trump told reporters without elaborating.

The Chinese state-run Xinhua News Agency reported Thursday that the national security law, created specifically for Hong Kong, will be discussed at China's annual session of its parliament starting Friday.

Hong Kong media reported that the law, which could be pushed through at the National People's Congress, would outlaw acts of separation, sedition, foreign interference and terrorism in the city.

If the law is enforced, people in Hong Kong who criticize the Communist-led Chinese government could be accused of secession, foreign affairs experts say.

The U.S. government has been against any activities that would undermine Hong Kong's autonomy as promised by Beijing.

Under the "one country, two systems" framework, Hong Kong was promised it would enjoy the rights and freedoms of a semi-autonomous region following the former British colony's return to Chinese rule in 1997.