China opposes the "Taiwan Travel Act" and urges the United States to adhere to the one-China policy and stop any official ties with Taiwan, the Foreign Ministry spokeswoman said on Wednesday.

Hua Chunying made the remark in response to a planned visit by a US diplomat to the island. Media reports say that Alex Wong, deputy assistant secretary in the Bureau of East Asian and Pacific Affairs at the US Department of State, will visit Taiwan from March 20 to 22.

It would be the first official visit since US President Donald Trump signed the act on Friday. It encourages visits between the United States and Taiwan at all levels.

Trump had pledged shortly after taking office to support the one-China policy.

According to Hua, China has initiated negotiations on the issue and urged the US to adhere to the three joint communiques between China and the US.

She also urged the US to halt official contacts with Taiwan and deal with Taiwan issues discreetly to avoid harming Sino-US relations and cross-Straits relations.

On Tuesday, An Fengshan, spokesman for the Taiwan Affairs Office of the State Council, condemned the recent "Taiwan independence" remarks made by the island's executive head.

An was responding to Taiwan-related remarks made by the island's "premier", Lai Ching-te. Lai called the island province a "sovereign and independent state".

"The remark that mentioned 'Taiwan independence' was a flagrant provocation to the cross-Straits relations," An said, adding that Taiwan separatists will suffer by their own hands.

"The mainland and Taiwan belong to one China. Taiwan is an inseparable part of China and has never been and will not become a country," An said.

The mainland has always held that the one-China policy is the political foundation for cross-Straits relations.

President Xi Jinping vowed on Tuesday to defeat secessionist attempts in his speech at the closing meeting of the 13th National People's Congress annual session.

"Chinese people have the resolve, the confidence and the ability to defeat secessionist attempts in any form," he said.

"Any actions and tricks to split China are doomed to fail. And these separatists' actions will be met with the condemnation of the people and the punishment of history."

Premier Li Keqiang warned on Tuesday at a news conference that China will not tolerate the attempts of any external force to use Taiwan as a card to cause difficulties for cross-Straits relations.

Regarding the new US law, the Chinese embassy in Washington said, "China is strongly dissatisfied with that and firmly opposes it."

"The relevant clauses of the 'Taiwan Travel Act' severely violate the one-China principle, the political foundation of the China-US relationship, and the three joint communiques between China and the US," according to a statement released by the embassy.

"We urge the US to adhere to the one-China policy and honor the commitments it made in the three joint communiques and to stop pursuing any official ties with Taiwan or improving its current relations with Taiwan in any substantive way," it said.

Ni Yongjie, deputy director of the Shanghai Institute of Taiwan Studies, said that trying to hold China in check with the "Taiwan card" is useless.

Zhou Jin contributed to the story.