The president said America had a “commitment” to go to the aid of the island, which complained of growing military and political pressure from Beijing, which claims a territory.
However, the White House later said there had been no change in position.
Washington has long followed a policy of “strategic ambiguity” over its military intervention to protect Taiwan in the event of a Chinese attack.
But asked in a town hall if the United States would get involved, Mr. Biden said: “Yes, we are committed to doing it. “
In August, an administration official was forced to insist that US policy towards Taiwan had not changed after the president appeared to suggest that the United States would defend the island in the face of to an assault.
Following Mr. Biden’s final comments, a spokesperson said, “We will continue to support Taiwan’s self-defense and we will continue to oppose any unilateral change in the status quo.”
In response to Mr Biden’s statement, Taiwan’s presidential office said its position was unchanged and remained the same and that it would not give in to pressure or “move recklessly” when it gets support.
“Taiwan will show a strong determination to defend itself,” said presidential office spokesman Xavier Chang, who also noted the continued “strong” support from the Biden administration.
Mr. Biden said people shouldn’t be worried about Washington’s military might because “China, Russia and the rest of the world know that we are the most powerful army in world history.”
He added, “What you need to worry about is whether or not they’re going to engage in activities that would put them in a position where they could make a big mistake.
“I don’t want a cold war with China. I just want China to understand that we are not going to back down, that we are not going to change any of our views. “
Tensions between Taiwan and China are at their worst in more than 40 years, Taiwanese Defense Minister Chiu Kuo-cheng said this month, stressing that Beijing would be able to mount a “large-scale” invasion by 2025.
Taiwan says it is an independent country and will defend its freedoms and democracy.
China has criticized what it called “collusion” between Washington and Taipei.
The country’s ambassador to the United Nations, Zhang Jun, said Beijing was pursuing “peaceful reunification” with Taiwan.
He said, “We are not the troublemaker.
“On the contrary, some countries – the United States in particular – are taking dangerous measures, leading the situation in the Taiwan Strait in a dangerous direction.
“Getting Taiwan into a war is definitely in no one’s interest. ”