Vice President Joe Biden told Japan on Tuesday that the U.S. was “deeply concerned” about China's declaration of a new air defense zone which covers islands claimed by both Tokyo and Beijing, and urged both sides to show restraint to ease tensions.

“We, the United States, are deeply concerned by the attempt to unilaterally change the status quo in the East China Sea,” said Biden at a joint press conference with Japanese Prime Minister Shinzo Abe in Tokyo, during the vice president's week-long trip to Asia.

“This action has raised regional tensions and increased the risk of accidents and miscalculation,” Biden continued. “We are closely consulting with our allies on this matter, here in Japan and in Korea.”

The vice president said the dispute “underscores the need for crisis management’ and “effective channels of communication between China and Japan to reduce the risk of escalation.”

He also vowed to raise the Obama administration’s concerns with “great specificity directly when I meet with Chinese leadership the day after tomorrow.”

Biden’s remarks come after China declared an air defense identification zone [ADIZ] over islands which Japan claims as part of their territory in the East China Sea. China ordered all aircraft flying through the zone to identify themselves and seek clearance from its military.

China’s move has angered the Obama administration which last week sent two B-52 bombers on an unannounced flight through the contested zone. China said they tracked the U.S. aircraft but made no effort to intercept them.

On Monday, White House press secretary Jay Carney said the U.S. did not accept the “legitimacy” of Beijing’s air zone claims. But the administration has also urged U.S. air carriers to follow China’s rules in order to protect civilian passengers on flights and avoid any confrontation.

“It's a provocative action, an uncoordinated action at a time tensions already are running high,” said a senior administration official about China’s air zone on Tuesday. “This is not the kind of thing that contributes to the greater peace and security in northeast Asia.”

The official added that the U.S. would urge China to “exercise restraint in terms of further provocative actions including how it implements its ADIZ procedures.”

“We're also calling on China to avoid any other destabilizing actions including a new ADIZ over contested territory without any prior consultation with potentially affected parties,” said the official.

This story was published at 7:31 a.m. and has been updated.