Japan's defense minister has elaborated on ongoing studies on whether his country should acquire the ability to carry out counterstrikes as part of efforts to fundamentally reinforce its defense capabilities.

The timing of launching counterstrikes is one of the focal issues, along with the question of whether a possible enemy's command and control functions should be among the targets.

Hamada Yasukazu told reporters on Friday that Japan can only exercise its right to self-defense when an enemy has "initiated" an armed attack.

He stressed that there is no change in the idea that pre-emptive attacks are not allowed under Japan's defense-oriented policy.

Hamada said the country should judge when an enemy has initiated an attack on a case-by-case basis and by assessing specific factors. He said the factors include the international situation, the enemy's expressed intent, and the method and type of attack.

The government and the ruling coalition parties are now studying the topic. The proposed counterstrike capabilities assume hitting a potential enemy's missile base to respond to ballistic missile launches. Some say command and control functions should also be targeted.

Based on the studies, the government plans to revise key defense documents, including the National Security Strategy, by the end of the year.