"China has communicated with related countries over the [Air Defense Identification Zone] ... and urges them to understand China's legitimate security concerns and right to self defense," the spokesman was quoted by China's official Xinhua News Agency as saying.
China declared the zone in a unilateral move questioned by the U.S., Japanese and South Korean governments. Parts of the air defense zone extend over the Diaoyu Islands, territory disputed with Japan.
The spokesman said Japan was responsible for stoking regional tensions regarding its claims to the islands, known in Japan as Senkaku.
A U.S. government official was quoted by CNN on condition of anonymity as saying a Tokyo visit this week by Vice President Joe Biden was to express the "rock-solid commitment to our allies."
China is calling on aircraft entering the zone to submit flight plans and identify themselves upon entry. Japan said it doesn't recognize Beijing's authority though Washington said it would comply.
U.S. and Chinese relations have turned frosty since the U.S. military adopted its so-called pivot to the region. The move is a re-alignment of U.S. military assets to the Asia-Pacific.