Research prepared for the United States Congress argues Australia could abandon its $368 billion AUKUS push to buy nuclear-powered submarines (SSNs), outlining several alternatives including US owned boats serving both nations.

According to the report published by the Congressional Research Service (CRS), billions of Australian dollars could instead be diverted to military capabilities for this country and the US, such as missiles and B-21 long-range bombers.

Under the AUKUS Pillar 1 plan, US and British nuclear submarines will rotate out of Western Australia from 2027, before Australia buys up to five second-hand Virginia class boats in the 2030s, and then begins constructing a new fleet known as SSN-AUKUS.

In the 105-page report, a number of policy options are presented including Australia no longer purchasing US submarines but instead having American boats perform missions on its behalf, while still continuing to design and build the SSN-AUKUS fleet.

"An alternative to Pillar 1 as currently structured would be a US-Australia military division of labour under which US SSNs would perform both US and Australian SSN missions while Australia invested in military capabilities for performing non-SSN missions for both Australia and the United States," the report reads.

"Australia, instead of using funds to purchase, build, operate, and maintain its own SSNs, would instead invest those funds in other military capabilities — such as, for example, long-range anti-ship missiles, drones, loitering munitions, B-21 long-range bombers, or other long-range strike aircraft.

"Under this variation, the size of the US SSN force would eventually be expanded above previously planned levels by eight boats (i.e., the planned eventual number of SSNs that Australia had planned to acquire)."

Using stark language, the report warns that the costs of AUKUS Pillar 1 for Australia could "reduce, perhaps significantly, funding within Australia's military budget for other Australian military capabilities" particularly if the project's budget blows out.

"If this were to occur, there could be a net negative impact on Australia's overall military capabilities for deterring potential Chinese aggression," the report says.

The CRS report claims no alternatives were ever considered by AUKUS partners and concludes by diverted spending elsewhere it would help "create an Australian capacity for performing non-SSN military missions for both Australia and the United States".

"There is little indication that, prior to announcing the AUKUS Pillar 1 project … an analysis of alternatives (AOA) or equivalent rigorous comparative analysis was conducted to examine whether Pillar 1 would be a more cost-effective way to spend defence resources".

Greens Senator David Shoebridge, a vocal opponent of AUKUS, says the proposals outlined in the congressional report appeared more like "a strategic surrender than a partnership".

"This division of power no doubt makes sense from a US perspective with Australia providing them with funds and bases and getting no actual submarines," he said.

"From an Australian perspective that looks far more like a strategic surrender than a partnership.

"For the US, the whole AUKUS deal always had at its heart US access to Australian real estate for their submarines, bombers and marines, with any marginal additional Australian capacity being very much secondary."

But Dr Elizabeth Buchanan, a senior fellow at the Australian Strategic Policy Institute, said the report merely illustrated there are a several pathways to achieve the overarching strategic intent of AUKUS.

"Throwing our toys out of the sandbox when informed, rigorous and contestable analysis is produced isn't where we need to be as a nation," she said.

"The alternative pathway outlined by the CRS indeed offers some logical options, and after all, this multi-decadal project will need all the optionality and flexibility it can get."