Two US B-52 bomber planes have flown near artificial islands claimed by China in the South China Sea.
BBC News reports the Pentagon says their mission continued despite being warned by Chinese ground controllers.
The incident comes ahead of a visit by US President Barack Obama to a summit in Manila next week, which China’s President Xi Jinping will also attend.
China is locked in maritime territorial disputes with several neighbours in the South China Sea.
China claims a large swathe of the resource-rich area and has been aggressively reclaiming land and building facilities on reefs, which the US and others oppose.
The US has said it plans to demonstrate its freedom of navigation principle in the sea, which challenges what it deems to be “excessive claims” to the world’s oceans and airspace.
