Defense Minister Nobuo Kishi and his Australian counterpart Linda Reynolds agreed Monday that the two countries will begin coordination to enable Japan to protect Australian military assets in noncombat situations.
The move comes as Japan and Australia are strengthening vigilance and surveillance activities amid China's growing assertiveness in the East and South China seas.
The protection by Japan's Self-Defense Forces of weapons and equipment belonging to foreign military forces became possible with the passage of new security legislation in 2015.
Australia would be the second country, after the United States, whose assets Japan would be allowed to protect under the law.
The law stipulates that SDF personnel are permitted to protect the military assets of other countries on condition that the foreign forces are engaged in activities contributing to the defense of Japan.
"We'll not engage in protecting (partners' assets) at the scene of combat," Kishi told reporters. "If it is recognized that an armed assault may occur, we'll order the suspension of such protection."
But a Japanese Defense Ministry official admitted that the protection could cover "gray zone" situations, such as if Australian vessels are being intimidated without an armed attack taking place.
"Australia is our special and strategic partner in the region. To maintain and enhance a free and open Indo-Pacific, we will increase our countries' cooperation and interaction," Kishi said earlier at a joint press appearance with Reynolds.
They said Japan, Australia and the United States are holding a joint military drill near the South China Sea through early Tuesday morning.
"Activities like this contribute to the regional security," Reynolds said.
In a joint statement released after their meeting in Tokyo, the ministers said they "reinforced their strong opposition to any attempts to unilaterally change the status quo by coercion" in the East and South China seas.
They also expressed concern about recent developments including "dangerous and coercive use of coast guard vessels...and efforts to disrupt other countries' resource exploitation activities," the statement said.
For the coordination of military asset protection, the Japanese and Australian defense authorities will promptly start discussions at the section chief and director levels.
On the situation in North Korea, they confirmed cooperation toward the elimination of weapons of mass destruction including ballistic missiles.
The two ministers also reaffirmed their countries' determination to prevent the evasion of sanctions by North Korea, including illegal ship-to-ship transfers and direct shipments of banned goods.