Prime Minister Kishida Fumio says Japan must set up a system that clearly shows its counterstrikes are not pre-emptive attacks, when the country faces missile attacks.
Kishida said at an Upper House budget committee meeting on Wednesday that Japan must be fully-equipped to protect people's lives and livelihoods amid rapidly evolving missile and other technologies.
He said Japan will keep working to boost its missile-interception systems, but other options, including capabilities to launch counterstrikes, should not be ruled out.
Kishida added that his government hopes to reach a conclusion on the matter by the end of the year, based on a report by a government panel of experts and discussions between the ruling parties, and others.
An opposition lawmaker argued that it is difficult to differentiate between counterstrikes and pre-emptive attacks.
The prime minister said there are various theories about pre-emptive attacks under international law, and yardsticks differ from country to country.
Kishida said Japan needs to establish a system that clearly shows its counterstrikes are not pre-emptive attacks.
He pledged his utmost efforts to provide explanations to the Diet and the public.