Beijing said Thursday it opposed military ties between Washington and Taiwan, after President Tsai Ing-wen confirmed a small number of US troops are present on the island.

Authoritarian China regards self-ruled Taiwan as its own territory and has vowed to one day seize it, by force if needed, and has ramped up its sabre-rattling in recent years.

On Thursday, Tsai said in an interview with CNN that there was a small number of US troops in Taiwan to help with training, adding she had "faith" that the American military would defend the island in the event of a Chinese attack.

The comments provoked ire from Beijing.

"We firmly oppose any form of official exchanges and military contacts between the United States and Taiwan, oppose US interference in China's internal affairs, and attempts to provoke and stir up trouble," said foreign ministry spokesman Wang Wenbin.

Tsai's comments are the first time a Taiwanese leader has publicly made such an admission since the last US garrison left in 1979 when Washington switched diplomatic recognition to Beijing.

"The one China principle is the political foundation of China-US relations," Wang added.

"The US should not underestimate the strong determination of the Chinese people to defend national sovereignty and territorial integrity."

Beijing has cut formal ties and ramped up diplomatic, economic and military pressure on Taiwan because Tsai does not regard the island as part of a "one China".

While the United States switched diplomatic recognition to Beijing it opposes any forced change to Taiwan's status and helps to maintain Taiwan's defensive capabilities.