China firmly opposes any form of official exchanges between the U.S. and Taiwan, and the U.S. will pay a heavy price for its wrongdoing on issues concerning China's Taiwan region, Zhao Lijian, spokesperson for China's Foreign Ministry, said on Thursday.

The remarks came as U.S. Ambassador to the United Nations Kelly Craft held video talks with Taiwan leader Tsai Ing-wen after Craft's planned visit to Taiwan was cancelled.

Reiterating that there is only one China in the world and Taiwan is an inalienable part of the Chinese territory, Zhao said the government of the People's Republic of China is the sole legal government representing China, stressing that it is a fact recognized by the international community.

China urges the U.S. to stop interfering in its internal affairs, Zhao said, adding that Craft's acts have severely violated the one-China principle and provisions of the three China-U.S. joint communiques.

"China will take all necessary measures to safeguard its interests," Zhao said.

Meanwhile, U.S. Under Secretary of State Keith Krach tweeted Wednesday that "@SecPompeo orders lifting of self-imposed restrictions with Taiwan by US Govt giving it Free Country status."

Zhao said Krach's remarks severely violated the basic norms of international relations, the one-China principle, the three China-U.S. joint communiques and the political pledge made by the U.S. on the Taiwan issue.

Zhao expressed strong opposition and urged the U.S. to stop manipulating the Taiwan issue, stop official contact with Taiwan and stop upgrading substantive relations with the region.