The $368 billion plan originally had Australia receiving three nuclear submarines from the US - two used and one new Virginia-Class vessels - before building its own in Adelaide.
But after changes to the deal, Australia will now get three used submarines from the US.
Foreign Minister Penny Wong said it did not matter whether the submarines were used or new.
"Whether it's two (used) and one (new) or three, it's the capability that matters," she told ABC Radio on Wednesday.
"We want three submarines to deal with, from the United States, to deal with a capability gap before the AUKUS submarines are to be delivered ... that is the plan."
Defence officials revealed at a federal budget inquiry Australia preferred to receive second-hand vessels from the US.
Defence secretary Meghan Quinn told the inquiry on Tuesday night a reworking of the AUKUS deal was a joint idea between Australia and the US.
"Australia's position is that we would have always ... had a preference for three in-service (submarines)," she said.
"There are many reasons why three in-service (submarines) would be simpler, lower-cost through the training of staff, the sustainment arrangements, the maintenance requirements, and all of those considerations."
Defence Industry Minister Pat Conroy said the change in the AUKUS deal did not mean a fundamental altering of the security pact.
"It will be cheaper, simpler to manage, and it's been confirmed by the Pentagon overnight," he told ABC Radio.
"We'll get submarines ... about six years into their 33-year life cycle. They'll be cheaper, they'll be really effective at that stage, and we'll be acquiring the most capable nuclear-powered conventionally armed submarines in the world."
Mr Conroy said Australia would save a "considerable" amount by not acquiring a new submarine, but did not disclose the cost.
He denied the used submarines would be more costly to maintain in the long term.
The comments come after Labor backbencher and former minister Ed Husic called for the government to rethink the multibillion-dollar plan.
Mr Husic said on Tuesday the deal also had to be rethought due to America becoming a more unreliable ally.
"You do wonder whether or not we will get the deal, even the reconfigured one that we have got," the western Sydney MP told reporters at Parliament House.
Senator Wong said the backbencher was entitled to his view on AUKUS.
"It is in the best interests of our country for this project to continue to proceed. We believe it is necessary for Australian security and we believe chopping and changing will only set the country back," she told ABC TV.
12°C