BEIJING -- China has lodged stern representations with the United States over a Taiwan-related bill, a Foreign Ministry spokesperson said over the weekend.

It was reported that US President Donald Trump on Friday signed the bill that encourages visits between the United States and China's Taiwan at all levels.

"We firmly oppose the US side signing the Taiwan Travel Act," spokesperson Lu Kang said.

"As has been pointed out many times by China, the relevant clauses of the act, though not legally binding, severely violate the one-China principle and the three joint communiques between China and the United States," Lu said.

The Taiwan Travel Act sends out very wrong signals to "pro-independence" separatist forces in Taiwan, Lu said, noting that China was strongly opposed to this.

"We urge the US side to correct its mistake, stop pursuing any official ties with Taiwan or improving its current relations with Taiwan in any substantive way, and handle Taiwan-related issues properly and cautiously so as to avoid causing severe damage to China-US relations and cross-Strait peace and stability," Lu said.

"Taiwan is a part of China and issues regarding Taiwan are completely internal affairs of China," said Wu Qian, spokesperson for the Ministry of National Defense.

Wu stressed that the bill had interfered in the internal affairs of China and injured the environment for the development of relations between the two countries' militaries.

"China demands that the US keep its promises, rectify its wrongs, refrain from implementing relevant clauses of the bill and stop seeking any official contacts, military ties or arms sales with Taiwan, so as to avoid doing serious harm to the China-US relationship, the ties between the two countries' militaries and the peace and stability across the Taiwan Strait," Wu said.