US Defence Secretary Chuck Hagel welcomes Japan's Defense Minister Itsunori Onodera during an honor cordon at the Pentagon, Friday, July 11, 2014.
Japan's annual defense white paper expresses strong concern about China's military build-up, citing its neighbor's increased airspace and maritime activities.
But officials say separately that Japan's defense budget may be insufficient to achieve the goals set by Prime Minister Shinzo Abe to bolster the country's military.
Abe's Cabinet in July approved a reinterpretation of Japan's war-renouncing constitution to allow the military to defend foreign countries and play a larger international role.
The annual report approved by the Cabinet on Tuesday says Japan is particularly concerned about China's establishment of an air defense identification zone extending to the disputed East China Sea islands that both countries claim. Japan scrambled jets in response to Chinese aircraft 400 times last year.