Japan took a "big leap" in using its defense forces to target China last year as the United States at the same time listed China as its greatest potential security challenge, according to a report from a Chinese think tank on Friday.

Observers said the military tension arose from territorial disputes, unease over China's rapid growth and attempts to use China as a scapegoat to justify a military buildup by Tokyo and Washington.

The annual report on Japanese military power, released by the China Strategic Culture Promotion Association, said two of the most eye-catching changes in Japan's defense forces in 2012 were Tokyo's efforts to normalize its defense power and to use it against China.