AUKUS speculation ramps up ahead of Anthony Albanese's US meeting

Some Defence experts say they're surprised over reports that Australia will purchase up to five US Virginia class nuclear powered submarines while waiting to acquire a fleet of nuclear-powered submarines based primarily on a new British design with American technology.

The Prime Minister, on a diplomatic mission in India, did not reject the rumours when pressed by reporters on Thursday.

Mr Albanese is due to appear at the San Diego Naval Base on Tuesday with his British counterpart and US President Joe Biden to officially announce the AUKUS details, on what appears to be two sub designs.

"I'll be making further comments about specific proposals at the appropriate time," Mr Albanese said.

"I look forward to announcing those details. They will be announced in the appropriate way."

The AUKUS deal has been described by Mr Albanese as the "single biggest leap in our defence capability" in Australia's history.

With questions raised about crewing and the foreign technology, he insists Australia would maintain its sovereignty if nuclear submarines were deployed in a regional conflict.

"Australia will retain, absolutely, our sovereignty. Absolute sovereignty. 100 percent," he said. "It is very important that Australia is a sovereign nation state ... and that's something that's respected by all of our partners as well."

Reports describe an ebullient British Prime Minister Rishi Sunak "delighted" that the UK had apparently won over the US design after 18 months of secret negotiations.

In the meantime, to address a capability gap, Australia would purchase three US Virginia class nuclear powered submarines in the 2030's, with an option for two more, raising questions about crewing.

Marcus Hellyer, head of research at Strategic Analysis Australia, said the two separate reports didn't quite stack up.

The defence procurement expert flagged it would take years of training for the Australian Defence Force to become well-acquainted with the off-the-shelf US submarines so it made little sense to dump them for another submarine shortly after.

"Capability transitions are always difficult. They're disruptive to militaries, they always create a lot of risks. They tend to create dips in capability and, if they're done badly, they can result in a loss of capability," Dr Hellyer said.

"It's sort of odd that you would do this - undertake this difficult journey twice essentially.

"If you've already transitioned to the Virginia class and brought that into service in Australia. Why would you go through a second transition?

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Questions have also been raised over how each country, and in particular Australia, will maintain sovereignty within the pact.

But Dr Hellyer agrees with the federal government position that Australia's sovereignty will be upheld.

"We're not signing a contract saying the US will deliver boats, and then there's a clause in there that says, and 'should the US go to war over Taiwan those Australian boats will be deployed to Taiwan,'" he said.

"But I think there's a very strong expectation on both sides that we will cooperate and work together in in times of conflict.

"That's the case whether we have [nuclear-powered submarines] or not."

The acting Prime Minister and Defence Minister Richard Marles took the occasion of the last parliamentary question time before the announcement to describe the imminent announcement as "a bipartisan moment of huge significance to our country.

"Australia will become just the seventh country to have the ability to operate a nuclear powered submarine," he told Parliament.

"We have never operated a military capability at this level before. This will be a massive industrial endeavour."

He and Opposition Leader Peter Dutton insisted the new subs will contribute to the peace and the stability of our region and of the world.

"Our neighbours should hear the very clear message that this is about providing peace and stability for our region," Mr Dutton told Parliament.

"We're not an aggressive nation. We're a nation that strives for peace."

A Reuters report cites anonymous officials saying the United States would forward deploy some submarines in Western Australia by around 2027 - a reference to the Indian Ocean HMAS Stirling (Fleet Base West) in Western Australia which has been home to the outdated Collins Class submarines.

A year ago, then-prime minister Scott Morrison announced $10 billion to build a new east coast submarine base to support future nuclear-powered submarines.

The three preferred east coast locations identified by Defence were Brisbane, Newcastle and Port Kembla.