The United States and close ally Japan have sharply criticized China's airspace declaration, with U.S. Defense Secretary Chuck Hagel calling it a "destabilizing attempt to alter the status quo in the region." He said on Saturday the United States would not change how it operated there.
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Experts said the Chinese move was aimed at chipping away at Tokyo's claim to administrative control over the area, including the tiny uninhabited islands known as the Senkaku in Japan and the Diaoyu in China.
Japan's two biggest airlines - Japan Airlines and ANA Holdings - bowed to a Japanese government request to stop complying with the Chinese demands for flight plans and other information. They will stop providing the information on Wednesday, spokesmen for the carriers said.
By demanding airlines file flight plans or risk being intercepted by military jets, China is forcing them to effectively acknowledge Beijing's authority over the Air Defense Identification Zone, which is about two-thirds the size of Britain.
But in persuading ANA, JAL and other carriers to ignore the zone, Japan's Primes Minister Shinzo Abe may be calling China's bluff.
Some airlines in the region did agree to begin complying with the Chinese identification measures.
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While Washington does not take a position on the sovereignty of the islands, it recognizes that Japan has administrative control over them and is therefore bound by treaty to defend Japan in the event of an armed conflict.
The Pentagon said the training exercise "involved two aircraft flying from Guam and returning to Guam." Warren said the U.S. military aircraft were neither observed nor contacted by Chinese aircraft.
China's Defense Ministry said on Monday it had lodged protests with the U.S. and Japanese embassies in Beijing over the criticism from Washington and Tokyo of the zone.
China also summoned Japan's ambassador, warning Tokyo to "stop words and actions which create friction and harm regional stability," China's Foreign Ministry said. Tokyo and Seoul summoned Chinese diplomats to protest.
In addition, China sent its sole aircraft carrier on a training mission into the South China Sea on Tuesday amid maritime disputes with the Philippines and other neighbors and tension over its airspace defense zone.
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It was the first time the carrier was sent to the South China Sea.
Australia summoned China's ambassador to express concern over its imposition of the Air Defense Identification Zone over the East China Sea, the foreign minister said on Tuesday, decrying the move as unhelpful in a region beset by tension.