Beijing on Wednesday strongly criticized Washington's "gross interference" in its domestic affairs after US President Donald Trump signed into law the Asia Reassurance Initiative Act of 2018 on Monday.

The section of the law on Taiwan reiterates the US commitment "to counter efforts to change the status quo and to support peaceful resolution acceptable to both sides of the Taiwan Strait" and calls on the US president to encourage the travel of high-level officials, as well as regular arms sales, to Taiwan.

"China is strongly unsatisfied with and firmly opposed to the US for insisting on signing the act into law," said Foreign Ministry spokesman Lu Kang, adding that it seriously violated the one-China principle and stipulations of the three China-US joint communiques.

"China has lodged solemn representations to the US side," he told a regular press conference in Beijing, urging Washington not to implement the law.

The US should prudently and properly handle Taiwan-related issues to avoid undermining China-US relations as well as the peace and stability across the Taiwan Straits, the spokesman said.

Also on Wednesday, President Xi Jinping stressed that the Taiwan question is a domestic affair that concerns China's core interests and the national bond of the Chinese people, and it allows no interference from the outside.

Xi made the remarks when delivering a speech at a gathering held in Beijing to commemorate the 40th anniversary of the issuing of the Message to Compatriots in Taiwan.

The statement, issued by the Standing Committee of the National People's Congress on the first day of 1979, proclaims major policies and principles of the peaceful reunification of China.