Former Liberal prime minister and AUKUS critic Malcolm Turnbull told an independent public inquiry into the agreement on Monday it was unlikely the Virginia-class submarines would be delivered to Australia when the US navy continued to fall behind on production.
Under the $368 billion deal, a future US president must certify that the sale of the boats won't negatively impact the American navy.
"In what political fantasy land is a president going to do that if they're already short," Mr Turnbull said.
"And we can't complain because ... the Americans have been utterly transparent about this.
"We won't have been double-crossed or reneged on or anything like that."
The crowdfunded inquiry is being overseen by former Labor minister and Midnight Oil frontman Peter Garrett.
Australia will buy three used Virginia-class submarines from the US, before the new SSN-AUKUS boats enter service from the 2040s.
The Albanese government confirmed earlier in August media reports that thousands of American military personnel will be deployed to Western Australia to support submarine rotations to HMAS Stirling.
The US has set up the framework for a military base in the state, establishing Naval Support Activity Stirling over the past few months.
While Labor insists it will not be a US base on Australian soil, the designation is how Americans refer to other overseas bases.
Mr Turnbull said the "reality is this will be a US base".
"It's not called a US base, but it is a US base," he said.
"This has never been discussed in the Australian parliament. There's never been an inquiry. These are momentous changes, and our parliament has led us now."
AUKUS was signed between the US, Australia and the UK in 2021 under former prime minister Scott Morrison and the Biden administration.
Former Labor foreign minister Bob Carr said the opportunity to have opted out of the security pact was the election of the Albanese government in 2022 which had a "clear opening" to question the deal.
He said the US will not be in any position in the 2030s to transfer the boats as originally planned.
