WASHINGTON (AFP) - The United States warned China on Thursday against sparking tensions in international airspace after Japan accused Beijing of "dangerous maneuvers" above disputed seas.

"We do not accept China's declaration of an ADIZ (Air Defense Identification Zone) over the East China Sea and urge China not to implement it," State Department spokeswoman Jen Psaki said in a statement.

"We continue to urge China to work with other countries to establish confidence-building measures, including emergency communications channels, which can address dangers and lower tensions." Japan has alleged that a Chinese fighter on Saturday flew within roughly 30 metres (100 feet) of a Japanese OP-3C surveillance plane above the waters where the countries' air defense identification zones overlap.

Another Chinese SU-27 fighter also flew close to a Japanese YS-11EB plane in the same airspace, the Japanese defense ministry said.

One fighter jet approached to within about 50 meters and the other was as close as 30 meters to the Japanese planes, according to the spokesman.

But Beijing hit back on Thursday at Tokyo's claims, saying two Japanese F-15 fighter jets came recklessly close to a Chinese Y-8 transport aircraft in an incident on November 23.

Ms Psaki said Washington urged all states "to ensure that they respect the safety of aircraft in flight." "Any attempt to interfere with freedom of overflight in international airspace raises regional tensions and increases the risk of miscalculation, confrontation, and unintended incidents," she maintained.

Relations between Japan and China are strained by a territorial dispute over Tokyo-controlled islands in the East China Sea known as Diaoyu in Chinese and Senkaku in Japanese.

Beijing raised regional tensions in November by declaring an air defense identification zone covering the area, which overlaps a similar Japanese zone.