Japan joining the AUKUS pact as an advanced technology partner would help share high end war fighting capability and act as a deterrent, the commander of the US military in the Indo-Pacific says.
Speaking at the Lowy Institute in Sydney on Tuesday night, Commander of the United States Indo-Pacific Command Admiral John Aquilino said potential adversaries needed to see the linkage of like-minded nations and the problem they would have if they tried to single-handedly take action in the region.
In a joint statement, the three AUKUS partners said they were considering working with Japan as part of advanced capability projects.
Asked what it would mean for Japan to join AUKUS' Pillar II, which focuses on hypersonics, AI and quantum computing, Adml Aquilino said he was supportive of capabilities being shared with Japan, Australia and the United Kingdom.
"It gets to the multilateral discussion ... the importance of having the broad set of like-minded nations being able to share high-end technologies to deliver war fighting capability, those things deliver deterrence," he said.
Under the partnership, Australia will acquire up to five Virginia class submarines in the 2030s, pending approval from the US Congress.
Asked about doubts raised that the US would not fulfil its promises under the AUKUS pact, Adml Aquilino dismissed the criticisms and declared his nation's commitment as "ironclad" and "bold and brave".
"I certainly admire the leadership for making the call and our commitment will deliver it," he said.
Asked if the nuclear-powered submarines could be used in a conflict involving Taiwan, the US commander said it would ultimately be Australia's call how those boats would be used.
Adml Aquilino said the stabilisation in the relationship between Australia and China was beneficial for the Indo-Pacific, but warned it might not last.
"I'm concerned that it's temporary," he said.
"I am hopeful that it will continue, but I do believe it is a tool that will be used again at the time and place of their (Beijing's) choosing."