Two US B-52 bombers flew over a disputed area of the East China Sea without notifying Beijing, despite China's bid to create an expanded "air defense zone," US officials said Tuesday.
The unarmed aircraft took off from Guam on Monday and the flight was previously scheduled as part of a routine exercise in the area, the defense officials said.
"Last night we conducted a training exercise that was long-planned. It involved two aircraft flying from Guam and returning to Guam," Pentagon spokesman Colonel Steven Warren told reporters.
No flight plan was submitted beforehand to the Chinese and the mission went ahead "without incident," with the two aircraft spending "less than an hour" in the unilaterally-declared Air Defence Identification Zone (ADIZ), Warren said.
A US defense official, speaking on condition of anonymity, confirmed to AFP the two planes were B-52 bombers.
China announced the expanded air defense zone amid a growing territorial dispute with Japan over an island chain in the East China Sea.
The area also includes waters claimed by Taiwan and South Korea, which also have both expressed their displeasure at Beijing's move.
Under the rules declared by China, aircraft are expected to provide a flight plan, clearly mark their nationality and maintain two-way radio communication to allow them to respond to identification inquiries from Chinese authorities.
Japan, the United States and several other governments have criticized China's announced air defense zone.