President Joe Biden said the US would defend Taiwan if China attacked, in an apparent departure from a long-held US foreign policy position.
But a White House spokesman later told some US media outlets that his remarks did not signify a change in policy.
The US has a law which requires it to help Taiwan defend itself.
But it has been deliberately vague about what it would actually do if China were to attack Taiwan, in what is known as “strategic ambiguity”.
China has yet to respond to Mr Biden’s comments.