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.

Prime Minister Shinzo Abe’s government has altered the nation’s postwar security policy over the past few years, most notably through new security laws that largely expand the range of activities permissible by the Self-Defense Forces.

Under its strictly defense-oriented policy, Japan has maintained that it cannot possess “attack aircraft carriers,” saying the vessels can be deemed offensive weapons that exceed the minimum capacity Japan needs for self-defense in light of the Constitution.

The Maritime Self-Defense Force has a fleet of flat-topped destroyers known as helicopter carriers. Its largest Izumo-class carriers are 248 meters long and can carry up to 14 helicopters.

F-35Bs can operate from existing helicopter carriers once modifications are made to the bow, deck and other areas, the sources said. These modifications will allow destroyers, new or old, to function as small aircraft carriers.

Japan has purchased F-35As for the Air Self-Defense Force and hopes to acquire 42 units. But the Defense Ministry is considering including F-35Bs in the purchase, or adding them onto the deal for the 42 F-35As.

The F-35B is the U.S. Marines variant of the F-35 multi-role fighter made by Lockheed Martin Corp. The F-35A has conventional takeoff and landing capability requiring a runway.