Defense Minister Itsunori Onodera and U.S. Defense Secretary Chuck Hagel on Wednesday shared their "strong concern" about China's establishment of an air defense identification zone over the East China Sea, saying it could lead to a confrontation.

"We agreed that China's one-sided action could trigger an unexpected incident and is extremely dangerous," Onodera told reporters after the telephone talks with Hagel.

Onodera said Tokyo and Washington see Beijing's latest move as counter to international law and will continue to cooperate on sharing information and conducting surveillance activities in the area where the Japanese-controlled Senkaku Islands are located.

"It's important to handle this issue resolutely and calmly through diplomatic efforts, and we agreed to send a message to China that its attempt to change the status quo will never be tolerated," Onodera said.

Their telephone talks came a day after a U.S. Defense Department official said two U.S. Air Force B-52s had flown into the ADIZ without informing Beijing.

The Chinese Defense Ministry said it was able to monitor and immediately identify the flight routes of the bombers in the zone.

Onodera defended the flights as part of normal operations and urged China to "immediately retract" the zone it established.

A high-ranking ministry official suggested the flights could be part of a U.S. strategy to demonstrate to China that its unilaterally declared ADIZ will not be accepted.

At issue is China's establishment Saturday of an ADIZ that covers the disputed, Japan-held Senkaku Islands in the East China Sea, drawing a strong protest from Tokyo. The U.S. government has also criticized China over the move.