SECURITY allies Washington and Tokyo expressed "deep concern" over Beijing's new Air Defence Identification Zone (ADIZ), which both called a unilateral attempt to change the status quo in the East China Sea.
The zone that China declared on Nov 23 dominated talks between visiting US Vice-President Joe Biden and Japan's Prime Minister Shinzo Abe here yesterday.
At a joint press conference after the meeting, Mr Abe again called for the ADIZ to be scrapped.
"We will not remain silent at the unilateral move by China to change the status quo by force. Under our strong Japan-US alliance, we will work closely to deal with the issue," he said.
Mr Biden said the US is deeply concerned about China's action, which "has raised regional tensions and increased the risk of accidents and miscalculation".
"This underscores the need for crisis management mechanisms and effective channels of communication between China and Japan to reduce risk of escalation," he said.
Mr Biden made it clear the US would stand by Japan when he said: "We will remain steadfast in our alliance's commitment."
China requires foreign planes to file their flight plans before flying through its ADIZ, and warns of "defensive emergency measures" if they do not cooperate.
Japan's two largest airlines complied, but stopped after the government told them not to.
The US Federal Aviation Administration, however, reminded US airlines to comply with requests by foreign governments.
Earlier in Washington, State Department spokesman Jen Psaki said China should rescind confusing ADIZ procedures that have raised the risk of accidents.
Mr Biden, whose three-nation swing began here on Monday, heads next to Beijing, where he is scheduled to hold talks with President Xi Jinping later today.
US officials briefing reporters said he would urge China to exercise restraint, for instance in how it implements ADIZ procedures.
In written answers to an interview with Asahi Shimbun daily, Mr Biden said the two neighbours need to take "crisis management and confidence-building measures to lower tensions".
Tokyo and Beijing are locked in a territorial dispute over a group of Japanese-controlled islands known as Senkaku, and which the Chinese call Diaoyu.
At their meeting, Mr Biden told his host: "The President and I agree that the US-Japan security arrangement is the cornerstone of our security, not merely in the Pacific region."
Mr Abe said Mr Biden's visit to Tokyo was timely, as the security environment had become increasingly severe.
Both countries agreed to work closely to achieve a deal on the Trans-Pacific Partnership free trade talks by year end.
A new round of negotiations is due to start in Singapore on Saturday.
They also agreed to proceed with the planned relocation of the US Futenma Airbase to another part of Okinawa to lighten the burden on local residents.
In Seoul, the third and last stop for Mr Biden, the government has said it would expand its own ADIZ in response to China's zone. But reports yesterday, quoting officials, said Seoul decided to delay any announcement.
"It will not be too late to make a decision once we see what cards Mr Biden will present during talks with Japan and China," said an official.