China’s latest assertion that the Taiwan Strait doesn’t qualify as international waters raises tensions over the nautical flashpoint, through which U.S. warships transit in a symbolic challenge to Beijing’s territorial claims over the democratically governed island.

While it’s unclear what Beijing means by "international waters,” the language may be intended to deter the U.S. from sailing through the strait, a practice that China has said harms stability and sends the wrong signal to "Taiwan independence forces.” Chinese officials have made such remarks repeatedly in meetings with U.S. counterparts in recent months, according to a person familiar with the situation, in what seems to be a change of position.

The U.S. on Tuesday backed Taiwan's assertion that the strait separating the island from China is an international waterway, rebuffing Beijing's claim to exercise sovereignty over the strategic passage.