Under the agreement, Australia will acquire three Virginia-class submarines from the US in the early 2030s before a new fleet of boats is built for delivery from the 2040s for a cost of $368 billion.
The three-nation partnership between the US, Australia, and the UK was signed in 2021 under former Liberal prime minister Scott Morrison and the Biden administration.
The Pentagon is now considering whether the pact is in line with US President Donald Trump's "America First" policy.
Mr Marles confirmed the US had advised Australia and the UK of the review.
While he did not guarantee Australia would receive the nuclear-powered boats from the US, he stressed he was confident.
Asked about contingency plans, should the deal sink, the defence minister indicated there were none.
"Chopping and changing guarantees, you will never have the capability ... There is a plan here, we are sticking to it, and we're going to deliver it," he told ABC radio on Thursday.
In an earlier statement, Mr Marles said it was "natural" that the Trump administration would want to examine such a major undertaking.Â
He also pointed to the UK's recently completed AUKUS review, which reaffirmed its support.
Critics of AUKUS point to the lagging production of boats in the US and have warned that the deal might jeopardise the US Navy's capabilities.
Australia handed over almost $800 million to the US in February - the first of a number of payments - to help boost the US submarine industrial base.
US Defence Secretary Pete Hegseth told Mr Marles during a meeting in Singapore this month that Australia should lift its defence spending to 3.5 per cent of gross domestic product, or output.
Australia's defence spending is on track to hit around 2.3 per cent of GDP by 2033/34.
Co-Chair of the Friends of Australia Caucus, US Congressman Joe Courtney, on Thursday warned against dumping the AUKUS deal.
"To walk away from all the sunk costs invested by our two closest allies - Australia and the United Kingdom - will have far-reaching ramifications on our trustworthiness on the global stage," he said.
Former Liberal prime minister Malcolm Turnbull, who's a critic of AUKUS, questioned why Australia wasn't conducting its own review given it had the most at stake.
"Our Parliament to date has been the least curious and least informed," he posted on the social media platform X (formerly Twitter).
"Time to wake up?"
Greens defence spokesman David Shoebridge said it was time for the government to open an inquiry into the "dud deal".
"We need an independent defence and foreign policy, that does not require us to bend our will and shovel wealth to an increasingly erratic and reckless Trump USA," he said.
Opposition frontbencher Bridget McKenzie said the US review was a "deeply concerning development" ahead of Prime Minister Anthony Albanese's departure for the G7 summit in Canada on Sunday.
Mr Albanese hopes to have a meeting with Mr Trump on the sidelines of the gathering in Alberta.
"Any undermining of this serious and substantial alliance between our two countries should be of grave concern to all of us," Senator McKenzie told Nine's Today show.
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