Tokyo: US Vice-President Joe Biden has delivered a carefully calibrated show of support for Japan, saying Washington is ''deeply concerned'' about Beijing's move to control airspace contested with Tokyo.
But he stopped short of demanding that China retreat, and urged the feuding neighbours to talk to each other.
Mr Biden's statement, at the start of an unexpectedly challenging trip to Asia that includes a stop in Beijing, captured the strategic complexities for the US in the tense showdown between Japan and China over disputed claims in the East China Sea.
US Vice President Joe Biden exchange smiles with Japanese Prime Minister Shinzo Abe at the start of their meeting at Abe's official residence in Tokyo.
China, Mr Biden said, was trying to "unilaterally change the status quo in the East China Sea", with an air defence identification zone that "raised regional tensions and increased the risk of accidents and miscalculation." He said he would raise the US concerns in detail when he met the Chinese leadership on Wednesday.
But rather than call for China to roll back its defence zone, as the Japanese government has urged it to do, Mr Biden said China and Japan needed "crisis management mechanisms and effective channels of communication" to avoid the risk of an accident or miscalculation.
"The only conflict that is worse than one that is intended is one that is unintended," he said, quoting his father, as an unsmiling Prime Minister Shinzo Abe stood next to him.
Mr Abe said the US and Japan would "not tolerate the attempt by China to change the status quo by force".
He said both countries reaffirmed that they would not alter any joint military operations because of China's zone.
"We will not condone any action that will threaten the safety of civilian aircraft."
That appeared to be an attempt to smooth over a disconnect between the US and Japan over the weekend, after the Federal Aviation Administration advised US carriers to identify themselves when entering the restricted zone. The Japanese government has instructed its carriers to ignore the Chinese demand.
Administration officials insisted there was no daylight between the US and Japan on how to respond to China's move. The FAA's guidance, they said, was no different than it would have been in any other case in which a country issued a warning to planes or ships.
"Nothing that FAA has done constitutes any acceptance or recognition of this," said a senior administration official traveling with Mr Biden.
"The US has clearly set forth that our military aircraft will continue to operate normally."
Administration officials said Mr Biden would urge China not to create any other such zones and to show restraint in policing this one. But neither the Vice-President nor his aides made any reference to asking the Chinese to rescind their action.
Japan perceives the Chinese air defence identification zone, which covers a wide swath of the East China Sea, as an attempt by the Chinese to assert control over a clump of disputed islands, known in Japan as the Senkaku and in China as the Diaoyu.
Japan has a long-established air defence identification zone of its own that covers much of the same area of the sea, including the islands. The dispute has raised tensions in the region to their highest level in nearly two decades.
In Beijing, a Foreign Ministry spokesman said China's defence zone fully complied with international law. He suggested China was open to the idea of establishing crisis-management mechanisms but added that Japan was not.
"The Japanese side unilaterally, on one hand, declares they want dialogue, but then they close the door to dialogue," he said.
For Mr Biden, the dispute has been a distraction on a trip that he hoped would cover a range of other issues, from a trans-Pacific trade agreement to the nuclear threat in North Korea.
New York Times