(CNN) -- Two U.S. Air Force B-52 aircraft on Monday flew into China's newly claimed air defense zone over the East China Sea without identifying themselves as China would have wanted, a U.S. official confirmed Tuesday.
This follows China's move last week to announce a new air zone over islands that both China and Japan claim.
The flights of the B-52s would not be a departure from the United States' previously stated intentions. Since China declared the new air zone last week, the United States said it would continue with its own air operations in the region and not recognize China's new restrictions, which require aircraft entering the zone to identify themselves and file flight plans.
The B-52s, which flew from Guam and returned there without incident, were not armed because it was a training mission. The mission lasted for several hours, but the aircraft were in the newly declared Chinese air zone for about an hour, according to the U.S. official.
The official declined to be named because of the sensitivity of the situation.