AUKUS, formed with both the UK and US in 2021 to address concerns about China's rising military ambition, is designed to enable Australia to acquire nuclear-powered attack submarines in the 2040s.
However, fears about the future of the $560 billion deal have persisted since the Trump administration initiated a review to examine whether it meets its "America-first" criteria.
Defence Minister Richard Marles and UK Secretary of State John Healey put pen to paper on a partnership and collaboration arrangement between the two allies on Saturday.
The so-called Geelong Treaty is being hailed as a historic pact in its own right, while also representing a 50-year co-operation arrangement under the AUKUS banner.
Mr Marles said the bilateral agreement built on "the strong foundation of trilateral co-operation between Australia, the UK and the United States" and advanced the shared objectives of AUKUS.
He remained confident of the future of US involvement in the partnership, he added.
"The Geelong Treaty will enable comprehensive co-operation on the design, build, operation, sustainment, and disposal of our ... submarines," Mr Marles said.
"It will support the development of the personnel, workforce, infrastructure and regulatory systems required for Australia's ... AUKUS program" as well as support the rotational presence of a UK Astute-class submarine at HMAS Stirling in Perth.
Speaking alongside Foreign Minister Penny Wong, Mr Healey and UK Foreign Secretary David Lammy in Sydney on Friday, Mr Marles said Australia had made two contributions of $A760 million each to AUKUS this year.
At the same press conference, Mr Lammy called Britain's relationship with Australia "an anchor in what is a very volatile world" and said it provided stability no matter which way geopolitical winds were blowing.
Mr Healey said the UK was confident it could meet its obligations on industrial capacity to deliver SSN-AUKUS submarines and was undeterred by the US review.
"Australia and the UK welcome the review because we see this as a chance for a new administration to renew their commitment to AUKUS and that's what we expect," he said.
Australia will pay $5 billion to support British industry in designing and producing nuclear reactors to power the future AUKUS-class subs.
It will also acquire at least three Virginia-class nuclear-powered submarines from the US in the early 2030s.
On Sunday, Mr Marles and visiting UK ministers will head to Darwin to observe joint military exercises known as Talisman Sabre, which comprise more than 30,000 personnel from 19 militaries.
The 2025 war games involve the UK's Carrier Strike Group, led by the Royal Navy flagship HMS Prince of Wales - the first UK carrier strike group to visit Australia since 1997.
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