The United States on Wednesday reaffirmed its military alliance with Japan and pledged to back Tokyo in a mounting dispute with China over a chain of small islands and the airspace over them.
Pentagon chief Chuck Hagel discussed the controversy in a call he initiated to Japanese Defense Minister Itsunori Onodera.
During their discussion on "the security situation in the East China Sea," Hagel criticized Beijing's establishment Saturday of what it called "the East China Sea Air Defense Identification Zone," according to Pentagon assistant press security Carl Woog.
The Chinese Defense Ministry on Wednesday described a different and somewhat more cautious route flown by unarmed B-52 bombers Tuesday than the route described a day earlier by the Pentagon on what it said was a routine training mission.
Chinese Defense Ministry spokesman Geng Yansheng said China "observed U.S. B-52 bombers" flying just inside the air defense zone.
Geng said the B-52s flew south and north along the zone's eastern border "from 11 a.m. to 1:22 p.m. Tuesday (local time), about 200 kilometers (124 miles) to the east of the Diaoyu Islands."
That route would mean the U.S. planes scarcely entered the new Chinese air zone and did not fly directly over the disputed islands.
In the Pentagon's previous account, the B-52 bombers flew about 3,000 miles from Andersen Air Force Base on the American island territory of Guam, circled the islands and returned to base. The mission required an in-air refueling.
Part of the vital air zone declared by Beijing is over eight small, uninhabited islands off China's eastern coast. Japan and China both claim control of the islands, which Japanese call Senkaku and the Chinese refer to as Diaoyu.
Hagel told Onodera that China's move "is a potentially destabilizing action designed to change the status quo in the region, and raises the risk of misunderstanding and miscalculation," Woog said.
Geng, however, said: "China is capable of exercising effective control over this airspace."
Vice President Joe Biden will address the controversy next week during a trip to Beijing.
"Clearly the visit to China creates an opportunity for the vice president to discuss direcdtly with the policymakers in Beijing this issue (in order) to convey our concerns directly and to seek clarity regarding the Chinese intentions in making this move at this time," a senior Obama administration official told reporters.
China also responded to the announcement Tuesday by major Japanese airlines that they will not share their flight data when their planes near the disputed air zone.
"We need to stress that China will identify every aircraft flying in the air defense identification zone," Geng said.
Hagel commended the Japanese government for exercising restraint in response to China's unilateral declaration.
"Secretary Hagel assured Minister Onodera that U.S. military operations will not in any way change as a result of China's announcement, noting that recent routine and long-planned U.S. flight operations have already occurred as normal following the (Chinese) announcement," Woog said.
Zhang Junshe, described by Xinhua as an expert with the Chinese Navy, told the news agency that establishment of the air defense zone is not targeted at Japan and is not tied to the two nations' dispute over the small islands.
"Other nations do not need to be alarmed," Zhang said.
Zhang noted that Japan, South Korea, the Philippines and Vietnam have set up their own air defense zones over waterways near their coastlines.
The new Chinese air zone partially overlaps with a previously established Japanese zone.
Chai Lidan, an expert with the Chinese Air Force, told Xinhua: "Since every country has an equal right to protect its sovereignty and security, the principle of 'first come, first served' should not be applied on air defense identification zones."
Liu Jieyi, Chinese Ambassador to the United Nations, told Chinese Central Television on Tuesday: "It's natural, it's indeed the right of every country to defend its airspace and also to make sure that its territorial integrity, its sovereignty are safeguarded."
But in his conversation with Onodera, Hagel "reaffirmed longstanding U.S. policy that Article V of the Japan-U.S. Mutual Defense Treaty applies to the Senkaku Islands and pledged to consult closely with Japan on efforts to avoid unintended incidents."