Former prime minister Scott Morrison says Australia's push to acquire nuclear submarines has always been about one thing: preventing war in the Pacific.
Mr Morrison said the acquisition of nuclear-powered submarines under the AUKUS pact with the US and UK would ensure any adversary preparing to attack Australia thought twice.
"AUKUS and the Quad were the two most significant checks on Chinese assertion in our region we had seen in 20 years," he told AAP.
Mr Morrison, who orchestrated the AUKUS agreement before it was publicly announced in September 2021, said AUKUS and the Quad - which includes the US, Japan and India - would be integral in counterbalancing Chinese aggression.
"I knew it would have a major impact on Australia's capability for generations," he said.
"All of these interlocking relationships and alliances and agreements ... are designed to do one thing - to ensure that no one thinks going to that next level is a good idea."
As speculation mounts over what submarine option the Albanese government will choose, the former prime minister said the original plan was to have the three nations put more nuclear submarines in the water.
"This wasn't about having one of these countries build our boats. This was about all three countries having more boats," he said.
"So we needed to look at something that would enhance that overall capability."
Defence Minister Richard Marles has echoed the language used by his US and UK counterparts that the new submarines will be "a genuine collaboration between all three countries".
Some reports suggest a British Astute class submarine with an American weapons system could be used.
Mr Morrison said while that option "doesn't make it a trilateral boat", an increase in interoperability should be welcomed.
"That may well mean that there are more US weapons on more British boats," he said.
"So that's good for the Americans. That's good for the British. The whole point of AUKUS was to boost everybody, not to drain any one for the benefit of the others."
A decision on the submarine project - the largest Australian defence purchase in history - is expected this month.
