The United States said Wednesday that it had advised U.S. airlines to take necessary steps to operate safely over the East China Sea as tensions rise between China and U.S. ally Japan because of new airspace defense zone rules imposed by Beijing.
State Department spokeswoman Jen Psaki said the U.S. is trying to determine whether the rules—which require planes flying near contested islands to identify themselves to Chinese authorities—cover other than military aircraft.
"We're attempting to determine whether the new rules apply to civil aviation and commercial air flight,'' Psaki told a daily briefing.
"In the meantime, U.S. air carriers are being advised to take all steps they consider necessary to operate safely in the East China Sea,'' she said. "Obviously, the safety of airplanes is key ... and we're looking into what this means.''
(Read more: Do airlines have the whole story on flight delays?)
Asked whether U.S. carriers would advise Chinese officials of their flight plans, Psaki said, "I wouldn't go that far—we're still looking at it.''
Deputy Secretary of State Bill Burns is set to meet Chinese Vice Foreign Minister Liu Zhenmin in Washington on Wednesday. Psaki said the meeting was planned long in advance.
The U.S. defied the new rules Tuesday by flying two unarmed B-52 bombers through the contested airspace. Pentagon officials said the bombers were on a routine training mission.
The new rules mean aircraft have to report flight plans to China, maintain radio contact and reply promptly to identification inquiries, as well as display clear markings of their nationality and registration.
Psaki had said Tuesday that the U.S., which has long encouraged Japan and China to resolve their territorial dispute through diplomacy, does not think nations should apply air defense identification zone procedures on foreign aircraft.
(Read more: Judge clears AMR-USAirways deal for takeoff)
"The United States does not apply that procedure to foreign aircraft, so it is certainly one we don't think others should apply,'' Psaki said.
Vice President Joe Biden will raise the issue during a visit to Beijing next week, senior U.S. officials said. Biden is set to visit China, Japan and South Korea during a weeklong trip.