Chinese military officials in recent months have repeatedly asserted that the Taiwan Strait isn’t international waters during meetings with U.S. counterparts, according to a person familiar with the situation, generating concern within the Biden administration.

The statement disputing the U.S. view of international law has been delivered to the American government by Chinese officials on multiple occasions and at multiple levels, the person said. The U.S. and key allies say much of the strait constitutes international waters, and they routinely send naval vessels through the waterway as part of freedom of navigation exercises.

China has long asserted that the Taiwan Strait is part of its exclusive economic zone, and takes the view there are limits to the activities of foreign military vessels in those waters. While China regularly protests U.S. military moves in the Taiwan Strait, the legal status of the waters previously wasn’t a regular talking point in meetings with American officials.