Japan could host Australian nuclear subs

Japan has offered to host Australia's nuclear submarines when they arrive as Tokyo's envoy extends further defence support to Canberra.

Ambassador Shingo Yamagami said Japan stood ready to co-operate on cutting-edge technology advanced under a military deal between Australia, the US and UK.

Mr Yamagami acknowledged Japan's place in the trilateral security pact may not be immediately obvious but the nation's security was tied to allies being able to deter potential adversaries.

"We are a frontline state facing challenging circumstances in the dangerous neighbourhood of Southeast Asia," Mr Yamagami told a defence conference on Monday.

Australia will acquire nuclear-powered submarines under the agreement, which Japan has offered to host.

"Such submarines will increase regional deterrence," Mr Yamagami said.

"Some measures are already in place to receive them should they come."

Assistant Defence Minister Matt Thistlethwaite said Japan was an important partner in the region when it comes to ensuring peace and stability.

"We certainly respect the role that Japan is playing within the region," he told the ABC.

"We'll seek to continue that relationship with Japan and other nations through the Quad."

The Quad dialogue includes Australia, India and the US with a focus on security in the Indo-Pacific.

Mr Yamagami reiterated the words of his prime minister Fumio Kishida that "Ukraine today could be East Asia tomorrow".

Mr Kishida told the East Asia Summit that China was continuously infringing on Japan's sovereignty and stoking regional tensions.

While not directly referring to China as a threat, Mr Yamagami spoke of the need for alliances to manage a more dangerous region.

"In other words, what matters to you matters to us too," he said.

Mr Yamagami said while technology such as hypersonic weapons wasn't at the level where outside nations could be brought into the tent, Japan stood ready to help.

"Japan's co-operation with AUKUS holds great potential," the ambassador said.

Former Australian ambassador to Washington Joe Hockey said Canberra would need to leverage private investment on a scale not seen outside of war to develop the military capabilities.

Mr Hockey told the conference the war in Ukraine had been "a failure of deterrence" by Europe, lambasting France and Germany for touting mediation and appeasement.

Former defence minister Kim Beazley called for a massive boost in defence spending, from six to eight per cent of the budget.