The US or the UK can exit the AUKUS agreement with a year's notice under a new arrangement, which requires Australia to legally protect both allies against costs or injuries arising from nuclear risks.
Documents tabled in parliament on Monday set out the agreed legal framework for transferring nuclear materials and equipment to Australia for the $368 billion acquisition of atomic-powered submarines announced in 2021.
The agreement, which will remain in force until 2075, says the AUKUS deal shouldn't adversely affect the ability of the US and UK to "meet their respective military requirements and to not degrade their respective naval nuclear propulsion programs".
"Any party may terminate the agreement ... by giving at least one year's written notice to the other parties," it reads.
The updated agreement means Australia will indemnify the US and UK from any "liability, loss, costs, damage, or injury (including third party claims)" arising from nuclear risks related to the program.
But the legal protection won't apply in relation to a conventionally armed, nuclear-powered submarine that has been in service with the US Navy "until such time as it is transferred to Australia".
Under the AUKUS deal, the US will sell at least three and up to five Virginia-class submarines in the early 2030s.
But the sales will be subject to approval.
Defence Minister Richard Marles said the nations had reached "another significant AUKUS milestone".
"It builds on the significant progress that has already been achieved, including the passing of the US National Defense Authorization Act, the announcement of Australia's sovereign submarine build and sustainment partners, and the ongoing work to integrate and uplift the industrial bases of all three AUKUS partners," he said.
Greens defence spokesman David Shoebridge blasted the new agreement for its "multiple escape hatches" which risked Australia being left high and dry.
"This is a $368 billion gamble with taxpayers' money from the Albanese government," he said.
"The new AUKUS agreement says that if at any point the United States thinks supplying material under the AUKUS agreement to Australia prejudices their defence, they can effectively terminate the agreement and pull out."
Senator Shoebridge said the US did not have enough nuclear submarines for its own purposes.
"What this agreement makes clear in black and white, that if the United States at any point, thinks they don't have enough submarines for themselves, they can pull out of AUKUS 2.0," he said.
