Kicking off a weeklong trip to East Asia, Vice President Joe Biden urged China and Japan to put in place new mechanisms to reduce the chance of an escalation in tensions.

The two countries, as we've reported, are at odds over air space above a set of disputed islands in the East China Sea. Back in November, China declared the air space to be part of its new, expanded air defense zone and any aircraft wanting to enter would first have to notify Chinese authorities.

The U.S. is obligated by treaty to defend Japan, so to send a message it crossed the air space with bombers. China sent warplanes of its own.

Today, Biden said the U.S. was "deeply concerned" and he urged calm.

"This action has raised regional tensions and increased the risk of accidents and miscalculation," Biden said during a news conference alongside Japanese Prime Minister Shinzo Abe, according to Reuters. "This underscores the need for crisis management mechanisms and effective channels of communication between China and Japan to reduce the risk of escalation."

On Monday, the White House called on China to drop its new procedures.

"The fact that China's announcement has caused confusion and increased the risk of accidents only further underscores the validity of our concerns and the need for China to rescind the procedures," White House spokesman Jay Carney said at his briefing.

The Wall Street Journal reports that Biden told a leading Japanese daily that he will discuss this issues with the leaders he meets with this week.

"I will reaffirm the strength of our alliance commitments and emphasize the importance of avoiding actions that could undermine peace, security and prosperity in the region," Biden said.

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