Australia's new conservative Government has backed moves to release Japan's military forces from constitutional restrictions limiting its operations to national self-defence.
Prime Minister Shinzo Abe wants a new policy of "active pacifism" that would allow a re-named defence force to operate abroad with allies and Defence Minister Itsunori Onodera has said Japan has the right to a military capable of pre-emptive strikes against an imminent threat.
Despite deep concern in China, Australia has backed Japan's development of a capability to boost its contribution to regional security.
Japan is locked into a close defence triangle with the United States and Australia.
Australian Prime Minister Tony Abbott met Abe at the East Asia Summit in Brunei, declaring Japan "Australia's closest friend in Asia" and inviting his counterpart to address federal parliament in Canberra.
Abbott told Abe he wanted to see Japan expand its international security role, including proposed developments for its defence force.
Japan this year lifted defence spending for the first time in a decade. Its troops have also edged around the constitution to take part in global peacekeeping operations, including missions in Iraq, East Timor, Pakistan, Cambodia and South Sudan.
Foreign Minister Julia Bishop expanded on Australia's shifting view during a visit to Japan this week.
Bishop told the Japanese National Press Club that Australia and Japan co-operated deeply on security and defence because of shared values and strategic interests, and the "mutually supportive" roles required as allies of the US.
"Against this background, we look forward to Japan making a greater contribution to security in our region and beyond - including through our alliances with the US," she said. "We support Japan's plan to work towards a more normal defence posture to help it play that greater role ...
"We work in partnership with Japan in many locations around the world, and if Japan is in a position to be part of our collective defence and security arrangements then I believe that that will be for the betterment not only for Australia, but the region and globe."
Other countries in the region, especially China, are wary of Abe's plans.
Although powerful, the Self Defence Force has little offensive capability and is constrained by the post-World War II constitution imposed by the US. Most Japanese oppose amendments.
Major moves to provide offensive capabilities would also require massive new funding, although this year's spending increase has been seen in the region as a potential shift to provide defence with a larger share of the national budget.
Tensions have risen dramatically between China and Japan over the disputed Senkaku-Diaoyu Islands and Japan has other territorial disputes with South Korea.
Both Japan and China are crucial trade and economic partners and Canberra is trying to conclude free trade agreements with each.
In an increasingly complex exercise to juggle emerging relations with China, Japan and the US, Canberra has defended its three-way security alliance with assurances that China is not the target, and has played down increasing co-operation with the US that includes the basing of a marine task force in Darwin.
"China's strength, China's growing strength is a benefit to the world, not a challenge," Abbott told Chinese President Xi Jinping in Brunei.