Beijing was responding to comments made by William Lai, who Taiwanese President Tsai Ing-wen chose as her vice presidential running mate for the coming election. Lai said on Monday that he is a “realistic worker for Taiwan independence,” adding that the state—officially called the Republic of China—is not “attached” to mainland China.

Taiwan—sitting just 80 miles from the Chinese coast across the Taiwan Strait—has acted as an independent nation for more than 70 years, having emerged from the last bastion of the nationalist forces that lost the Chinese Civil War to the Communist Party. It was made the Republic of China’s capital in 1949.

But China does not consider Taiwan to be an independent nation, and under its “One China” policy has vowed to bring the island back under Beijing’s control, whether by diplomatic or military means.

Beijing is deeply sensitive to any sentiment from Taiwan pushing for formal independence. Tsai and Lai’s Democratic Progressive Party has traditionally supported formalizing Taiwanese autonomy from the mainland, though Tsai has said she is not currently pushing to change the current balance.

China’s Taiwan Affairs Office said Thursday that it still considers Taiwan to be part of China, and warned that any suggestion otherwise presents a great risk for the island.

“‘Taiwan independence’ is a dead end, and it will only bring profound disaster to Taiwan,” the office said, according to Reuters.

“It will surely be opposed by all Chinese people, including Taiwan compatriots,” it added, adding that reunification of the two countries cannot be stopped by any nation or force.

The Taipei Economic and Cultural Office in New York—one of the sub-offices of Taiwan’s de facto U.S. embassy in Washington, D.C.—told Newsweek that China “unfortunately, has failed to understand” the “vibrant and functional democracy” on the island.

“Taiwanese people cherish their democratic way of life and will not be intimidated by China’s threats,” the statement added.

“They will make their own decisions at the polls next year and our government will continue to safeguard their right to do so. China’s threats have not worked before; they only strengthen our resolve to defend democracy.”

Lai—who last year described himself as a “political worker for Taiwanese independence”—voiced his support for independence on the same day China sailed an aircraft carrier through the Taiwan Strait, in a move Taipei described as an effort to intimidate the island.

Tsai has previously warned that Chinese military activity in the Strait is increasing and said this week that China is interfering in the ongoing electoral race daily. “China’s use of various ways of interfering in Taiwan’s elections is undermining our democracy,” she added, according to Liberty Times.

Tsai’s DPP currently holds a comfortable opinion poll lead over her main opponent—Han Kuo-yu of the China-friendly Kuomintang party—who has described formal independence as being worse than syphilis, Reuters noted.

This article has been updated to include comment from the Taipei Economic and Cultural Office in New York.