Defence Minister Itsunori Onodera said on Friday that his ministry is studying whether F-35B fighter jets can be put on a “helicopter carrier”, a move that may raise concerns that Japan is moving even further away from its strictly defensive policy.

Under the post-war pacifist constitution, the government has maintained that it cannot possess “attack aircraft carriers” as they are among what can be deemed as offensive weapons exceeding what is necessary for self-defence. Japan now has flat-topped destroyers that carry helicopters, but not fighter aircraft.

Onodera emphasised at a parliamentary committee that the study involving the use of the helicopter carrier Izumo, Japan’s largest post-war naval vessel, is being conducted for the purpose of “basic information gathering” and not “on a premise that F-35Bs will be introduced”.

Prime Minister Shinzo Abe said at the same committee: “It is a matter of course that we study what possibilities can be foreseen in dealing with crises and constantly consider [what we need].”