Chairman of the State Duma International Affairs' Committee Alexei Pushkov regards as dangerous the tendency to the expansion of air defense zones in the China-Japan-South Korea triangle.

"A competition has begun in the China-Japan-South Korea triangle in establishing air defense zones. It is dangerous - the U.S. and its allies have entered a war of nerves with China," he twitted on Sunday.

Earlier South Korea announced the expansion of its air defense zone.

According to Western media reports, the expanded South Korean zone overlaps with the Chinese in the East China Sea and in some parts with the Japanese zone.

Meanwhile, the U.S. State Department stressed that Seoul had discussed the possible expansion with Washington in advance.

"We appreciate (Republic of Korea) ROK's efforts to pursue this action in a responsible, deliberate fashion by prior consultations with the United States and its neighbors, including Japan and China," said U.S. State Department spokesperson Jen Psaki.

In November China announced the introduction of a special aircraft identification zone in the East China Sea to guarantee the air defense of the country which includes Senkaku islands which are a disputed area between Tokyo and Beijing. This sharply aggravated relations between Japan and China.

Last Wednesday ahead of the visit of U.S. Vice President Joe Biden to Beijing the Chinese Defense Ministry expressed readiness to exercise full control over the identification zone and take resolute action to this end.

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