Over the next two or three weeks, Japanese Prime Minister Shinzo Abe's Cabinet is expected make a decision on whether to revise the government's stance on Japan's right to exercise collective self-defence, said a key security adviser to Abe on Wednesday.
In an interview with Reuters, Shinichi Kitaoka said Japan should change its constitution to allow its military to defend not only its ally the United States, but also other countries close to it.
If so, this would be a step further than expected.
During his recent overseas trips, Abe sold his doctrine of "active pacifism" and asserted Japan's right to collective self-defence in aid of US forces.
Japan's envisioned right of collective self-defence could cover Southeast Asian countries and sea lanes of vital interest to the country.
"If US vessels, Australian vessels or Indian vessels that are protecting this sea lane were attacked and this has a very big impact on Japan, then Japan has the right to cooperate with those countries and remove it (the threat)," Kitaoka was quoted by Reuters as saying.
Abe is stepping up efforts to change the government's traditional interpretation of Article 9 of its constitution.
The war-renouncing article holds that Japan cannot exercise the right to collective self-defence - the use of military power to repel attacks on a country that has close ties with Japan even if Japan is not directly attacked.
Successive heads of the Cabinet Legislation Bureau have said in parliament that collective self-defence goes again Article 9, a position shared by the previous government.
Abe has appointed Komatsu Ichiro, a supporter of the principle of collective self-defence, as the bureau's new director general.
On the one hand, the Abe administration is expected to expand the scope of Japanese military activities, removing the legal and other constraints.