TOKYO (AFP) - Japan and China must set up systems for talking to each other and dealing with crises if they are to avoid a worsening of their territorial dispute, US Vice President Joe Biden said on Tuesday.

Mr Biden, in Tokyo at the start of a three-nation tour of Asia, said he will be talking "in great specificity" with Chinese leaders about the row over Beijing's declaration last month of an air defence zone in the East China Sea.

"This underscores the need for crisis management mechanisms and effective channels of communication between China and Japan to reduce risk of escalation," he told a joint press conference with Japanese Prime Minister Shinzo Abe.

"I will be raising these concerns in great specificity directly when I meet with the Chinese leadership the day after tomorrow," he said.

Mr Biden's visit comes as relations between China and Japan are at their lowest point in years, with both sides sending fighter jets to shadow the other's planes over the newly declared air defence identification zone.

Beijing now claims the right to issue orders to aircraft over a swathe of the sea, including over islands disputed with Tokyo.

Mr Biden vowed that the United States, which has a security treaty that compels it to come to Japan's aid if it is attacked militarily, would stand by its ally.

"We will remain steadfast in our alliance's commitment," he said.