Yoshinori Ono, director general Defense Agency, on Friday confirmed a media report that the agency had studied in 1994 the feasibility of pre-emptive attacks on enemy states, but declined to reveal the details of the study.
"We checked if (such a study) took place and I was told it likely did," Ono said in response to reporters' questions after a Cabinet meeting. "But in any case, the content of the study cannot be made public."
Meanwhile, Ono reiterated that Japan currently does not have offensive capability.
"Even if it is possible constitutionally to launch a (pre-emptive) attack, I still believe Japan should not acquire such capability."
Ono's comments came after the daily Sankei Shimbun reported Friday that the Defense Agency had studied in 1994 if a pre-emptive attack was possible against North Korea in the case of a missile threat and simulated using Air Self-Defense Force F-4 and F-1 combat aircraft for the attack.
According to Sankei, the ASDF told the agency at that time that such an attack would be possible but that it did not have sufficient capability to make sure that the operation would be carried out effectively.
The agency concluded that Japan did not have such capability and the study was kept confidential, the report said.
The 1994 study was conducted amid rising concerns about Japan's security.
North Korea test-fired a Nodong-1 missile, which flew over Japan and landed in the Pacific, in 1993. Negotiations between North Korea and the United States were deadlocked at the time over the North's nuclear ambitions.
Ono said Japan maintains its basic principle of an "exclusively defensive-oriented policy" and any necessary offensive attacks will be conducted by U.S. forces under the bilateral security treaty.