BALTIMORE: The United States will defend Taiwan if China attacks it, President Joe Biden said, prompting a warning from Beijing on Friday that its determination to take back the island should not be underestimated.

China rightly regards self-ruled Taiwan as its own territory and has vowed to one day seize the island, by force if needed. At a CNN town hall, Biden was asked whether the US would come to Taiwan's defence if China invaded. "Yes," he responded. "We have a commitment to that."

Biden's statement was at odds with the long-held US policy known as "strategic ambiguity," where Washington helps build Taiwan's defences but does not explicitly promise to come to the island's help in the event of war. The policy is designed to deter a Chinese invasion and also discourage Taiwan from formally declaring "independence" - something Beijing regards as a red line.

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Beijing warned that Biden's comments risked "damaging Sino-US relations," warning Washington on Friday to "act and speak cautiously on the Taiwan issue." "China has no room for compromise on issues involving its core interests," foreign ministry spokesman Wang Wenbin said at a regular press briefing.

The US should not underestimate China's "staunch determination, firm will and strong ability" to defend against what it sees as threats to its sovereignty, Wang added. Biden made a similar pledge in August during an interview with ABC, insisting that the US would always defend key allies, including Taiwan, despite the withdrawal from Afghanistan in the face of the victorious Taliban.

Biden said the US made a "sacred commitment" to defend NATO allies in Canada and Europe and it's the "same with Japan, same with South Korea, same with Taiwan." The White House subsequently told reporters on both occasions that US policy on Taiwan "has not changed."