As tensions mount between China and Taiwan, U.S. President Joe Biden has spoken on the phone to Chinese President Xi Jinping.
Biden told reporters on Tuesday that both leaders had agreed to keep to the Taiwan agreement.
An apparent reference to Washington's policy of recognizing Beijing rather than Taipei on the expectation that the future of Taiwan will be determined be peaceful means.
"I've spoken with Xi about Taiwan. We agree ... we'll abide by the Taiwan agreement...We made it clear that I don't think he should be doing anything other than abiding by the agreement."
China claims Taiwan as its own territory and has not ruled out the possible use of force to achieve unification.
The island, which broke away from the mainland in 1949, rejects Beijing's claims and has its own democratically elected government.
Over a four day period beginning last Friday, Taiwan reported close to 150 Chinese air force aircraft entered its air defense zone.
The show of force from Beijing has been condemned by Washington and Taipei.
Taiwan's defense minister said on Wednesday China will be capable of mounting a full scale invasion by 2025, adding that relations were at the worst level in more than 40 years.