President Joe Biden said the US would defend Taiwan if China attacked, in an apparent departure from a long-held policy.
"Yes, we have a commitment to do that," he said when asked during a townhall if the US would defend Taiwan.
But a White House spokesman later told some US media outlets that his remarks did not signify a change in policy.
Taiwan reacted by saying Mr Biden's statement would not change its own position with regards to China.
The US has long practised "strategic ambiguity" when it comes to the thorny issue of defending Taiwan.
This has meant the US has been deliberately ambiguous about what it would do if China were to attack the island.
China sees Taiwan as a breakaway province, one that it may take back by force one day if necessary, whereas Taiwan claims that it is a sovereign state.
The US has no official diplomatic ties with Taiwan, but sells arms to it as part of its Taiwan Relations Act, which states that the US must help the island defend itself.
Taiwan's presidential office responded to Mr Biden's statement by saying it would neither give in to pressure nor "rashly advance" when it gets support.
"Taiwan will show a firm determination to defend itself," said presidential spokesperson Xavier Cheng, who also went on to acknowledge the Biden administration's continued show of 'rock-solid' support for Taiwan.
Tensions have been rising between Taiwan and China in recent weeks after Beijing flew dozens of warplanes into Taiwan's air defence zone.
Mr Biden added that he was not worried about an intentional conflict with China, and said there was no need to "worry about whether they're going to be more powerful" because "China, Russia and the rest of the world knows we're the most powerful military in the history of the world".
"What you do have to worry about is whether or not they're [China] going to engage in activities that would put them in a position where they may make a serious mistake," he said.
When queried a second time by CNN's Anderson's Cooper about whether the US would come to Taiwan's defence in the event of an attack by China, Biden again answered in the affirmative.
A White House spokesperson later attempted to clarify Biden's comments to US media outlets, saying the US was "not announcing any change in our policy and there is no change in our policy".
Source: BBC