President Joe Biden says the United States would come to Taiwan's aid and has a commitment to defend the island that China claims as its own territory.
"Yes, we have a commitment to do that," Mr Biden said at a CNN town hall when asked if the US would come to Taiwan's defence.
Mr Biden said people should not worry about Washington's military strength.
"China, Russia and the rest of the world knows we're the most powerful military in the history of the world," he said.
"What you do have to worry about is whether or not they're going to engage in activities that would put them in a position where they may make a serious mistake."
Military tensions between Taiwan and China are at their worst in more than 40 years, Taiwan's Defence Minister, Chiu Kuo-cheng, said this month, adding that China would be capable of mounting a "full-scale" invasion by 2025.
China claims Taiwan as its own territory, which would be taken by force if necessary.
On the other hand, Taiwan says it is an independent country and will defend its freedoms and democracy.
China says US is taking 'dangerous actions'
China says Taiwan is the most sensitive and important issue in its ties with the United States and has denounced what it calls "collusion" between Washington and Taipei.
Speaking to reporters, China's United Nations Ambassador Zhang Jun said they are pursuing "peaceful reunification" with Taiwan and responding to "separatist attempts" by its ruling Democratic Progressive Party.
"We are not the troublemaker. On the contrary, some countries — the US in particular — [are] taking dangerous actions, leading the situation in Taiwan Strait into a dangerous direction," he said.
"I think at this moment what we should call is that the United States to stop such practice. Dragging Taiwan into a war definitely is in nobody's interest. I don't see that the United States will gain anything from that."
US aims to show responsible handling of China ties
Mr Biden's comments come as White House officials are gearing up for a virtual meeting between the President and Chinese leader Xi Jinping.
They hope the meeting will show the world that Washington can responsibly manage relations between the rival superpowers, people familiar with the matter say.
The two sides agreed during talks in Switzerland this month to hold the virtual conference by the year's end, with direct leader-level communication intended to set relations in a more "constructive direction", a senior US administration official said at the time.
Combative diplomatic exchanges with China early in the Biden administration unnerved allies and US officials say direct engagement with Mr Xi is the best way to prevent the relationship between the world's two biggest economies spiraling toward conflict.
Given China's domestic COVID-19 restrictions and Mr Xi's reluctance to travel, two sources familiar with the matter said Washington was aiming for a video conference call between President Biden and President Xi in November.
They said plans were still under discussion.
An agenda would likely not be set until after consultations with allies, they said, including during next week's summit of the Group of 20 countries in Rome and a subsequent UN climate conference in Glasgow.
With disagreements abounding, US officials insisted it was a mistake to see a "thaw" in relations.
The administration has recently expressed concern about evidence of a nuclear build-up by China and its work on hypersonic missiles, and has also accused China of ramping-up military activity in an effort to intimidate Taiwan.
On Wednesday, Mr Biden's nominee to be ambassador to China, Nicholas Burns, called China Washington's "most dangerous competitor" and said the US needed to work closely with its allies.
"We have partners who believe in us and the Chinese really do not," he said.
"I think President Biden has tried to emphasise the need for us to be very closely aligned … [with] our treaty allies, our defence partners."
Reuters
