In what could be a major change in Japan's policy on aircraft carriers, the Defense Ministry is mulling a plan to buy F-35B stealth fighter jets for use on its helicopter carriers, government sources said.

The introduction of F-35Bs, which have short takeoff/vertical landing (STOVL) capability, will be useful in countering China's growing maritime assertiveness. They are expected to bolster Japan's ability to defend far-flung islands in the southwest, where only short runways exist, the sources said Sunday.

The move, however, is likely to trigger a backlash from China and Japan's other neighbors because it could be viewed as contradicting Japan's so-called "exclusively defense-oriented policy" under the pacifist Constitution.