Japan is considering whether a preemptive strike on North Korean missile bases would be an acceptable form of self-defence under the pacifist Japanese constitution, the government spokesman said on Monday.
"If we accept that there is no other option to prevent an attack ... there is the view that attacking the launch base of the guided missiles is within the constitutional right of self-defence.
We need to deepen discussion," Chief Cabinet Secretary Shinzo Abe said. Abe added that the ruling party might take up the matter internally.
Japan's Constitution currently bars the use of military force in settling international disputes and prohibits Japan from maintaining a military for warfare.
Tokyo, however, has interpreted that to mean it can have armed troops to protect itself.
Prime Minister Junichiro Koizumi said Monday that the international community must be united in saying that North Korea's missiles launches last Wednesday were wrong, a news report said.
Koizumi told an internal Liberal Democratic Party committee that Japan was working at the UN Security Council to produced a unified global response, Kyodo News agency reported.
"We are responding (to the launches) at the UN Security Council in a way that will enable the international community to unite and say that 'it's wrong for you do such a thing," Koizumi told members of his Liberal Democratic Party, Kyodo News agency reported.
Japan is pushing a UN resolution condemning North Korea for the launches and imposing sanctions on the communist nation.
On Sunday, Defense Agency Chief Fukushiro Nukaga told reporters that Japan needs to move forward on debate over whether having first-strike capabilities would still be within the bounds of the constitution, a news report said.
"It's only natural as an independent country that people should think we ought to have some minimal capability within a fixed framework," Nukaga said, according to Kyodo News agency.
Japan's ruling Liberal Democratic Party has long pushed for a constitutional revision to make it easier for its military to fight if the country came under attack.
Tokyo currently interprets the constitution in a way that allows the existence of its 240,000-strong Self-Defence Forces.