TOKYO (AP)— U.S. Vice President Joe Biden voiced strong opposition Tuesday to China's new air defense zone above a set of disputed islands, showing a united front with an anxious Japan as tension in the region simmered.

Standing side by side in Tokyo with Japanese Prime Minister Shinzo Abe, Biden said the U.S. is  "deeply concerned" about China's attempt to unilaterally change the status quo in the East China Sea.

"This action has raised regional tensions and increased the risk of accidents and miscalculation," he said.

Biden said the U.S. is coordinating closely with allies Japan, South Korea and others, adding that the U.S. has an interest in lowering tensions in the region.

"I will be raising these issues with great specificity when I meet with Chinese leadership the day after tomorrow," Biden said.

Biden's remarks came as Japan is pressing the U.S. to more actively take Japan's side in an escalating dispute over China's new air defense zone above a set of contested islands in the East China Sea.

The U.S. and Japan have refused to recognize China's air defense zone above tiny islands that China and Japan both claim. The U.S. and its allies are concerned China's move is part of a broader strategy to assert increasing authority in the region.

"The prospect for miscalculation and mistake is too high," Biden said of the air defense zone.

Abe, who met with Biden at the prime minister's residence here Tuesday, said he and Biden confirmed that neither country would tolerate the attempt to change the status quo by force. He invoked Japan's decades-long alliance with the U.S. in pledging the two would work closely to deal with the situation.

At the same time, Abe appeared to try to smooth over a minor rift that emerged between the U.S. and Japan as Biden headed to the region over whether commercial airlines should comply with China's demand that they file flight plans before flying through the zone. Japanese leaders were concerned after word came that the U.S. was advising American carriers, in line with existing protocol, to comply with such requests from foreign governments.

"We agreed we will not condone any action that could threaten safety of civilian aircraft," Abe said.

Reluctant to cede any ground, Tokyo has been urging Japanese commercial flights not to notify China before flying through the zone. Word that the U.S. had advised American commercial carriers to comply rankled leaders in Tokyo, who are hoping a united front with the U.S. will increase pressure on Beijing to reverse course.

But senior Obama administration officials said Tuesday that the U.S. never told American commercial carriers to comply specifically with China's demands. Rather, the Federal Aviation Administration merely reaffirmed existing policy that pilots should comply with such instructions anywhere in the world, said the officials, who weren't authorized to comment by name and demanded anonymity.

The zone covers more than 600 miles from north to south, above international waters separating China, South Korea, Japan and Taiwan. China says all aircraft entering the zone must notify Chinese authorities beforehand or face unspecified defensive measures.

Although the U.S. has joined Japan and other allies in refusing to recognize the zone, Washington has treaded carefully, wary of creating a new fault line in its relationship with China just as the U.S. is pursuing a new era of economic cooperation with Beijing.

The show of unity between Biden and Abe will be closely watched by China, as well as other Asian nations worried that the new defense zone may portend further steps by China to assert control in the region. On Monday, China's ambassador to the Philippines claimed China has a sovereign right to establish a similar zone over the South China Sea, where China and the Philippines are locked in another long-running territorial dispute.

The feud promises to trail Biden throughout his weeklong trip to Asia _ a tour intended to affirm Washington's continued interest in upping its presence in the region, in part to counter China's growing influence.

After a working dinner with Abe on Tuesday night, Biden will fly to Beijing on Wednesday to meet with Chinese President Xi Jinping, where officials said Biden would raise U.S. concerns over the zone directly. Biden will then travel Thursday to South Korea - another U.S. ally at odds with China over the air defense zone.