Coalition vows not to go nuclear on Labor subs choice

Opposition Leader Peter Dutton has pledged the coalition will back the Albanese government's choice of nuclear submarine, despite insisting US vessels are the best option.

Prime Minister Anthony Albanese is expected to travel to Washington this month to announce alongside US President Joe Biden and UK Prime Minister Rishi Sunak which submarine Australia will acquire under the AUKUS security pact.

Mr Dutton has repeatedly said the American Virginia-class submarines are the quickest and cheapest option for Australia as speculation mounts an under-development British boat will be chosen.

But he said the government will receive bipartisan support for its decision.

"Labor's going to make a decision about which submarine they go with, but we'll support whatever decision they take," the former defence minister said.

Mr Dutton said his preference for the US model was "no slight on the Brits".

"The Brits have been allies of ours forever and for the sake of our country I hope that's always the case of the future," he said.

Defence Minister Richard Marles said Mr Dutton was basing his opinion on old advice and it was critical that there be cross-party support for the defence program.

"The opposition leader is obviously giving comments based on confidential advice he was provided almost a year ago - a lot of water has gone under the bridge since then," he said.

"We're really very much on the verge of an announcement and I think what matters now is - when that announcement is made - making sure that enjoys the support of the full spectrum of politics in Australia."

Mr Marles said the government would provide the opposition with briefings on AUKUS prior to the announcement.

During a visit to the Avalon air show in Victoria earlier this week, Mr Dutton warned against acquiring the nation's future fleet from the UK.

He said the American submarines were an established design and did not bring the risks of delays and blowouts that a new vessel could bring. 

Former independent senator and submariner Rex Patrick said Mr Dutton was right in his assessment of the submarines, but his comments were also about political differentiation from Labor.

Mr Patrick said a lot of work was required to support the nuclear submarines.

"When we can get our first boat it may well be that we simply are not ready to receive them from the Australian end," he said.

"We're going to have to start looking at how we make sure those reactors are safe, how much work are we going to be doing here in Australia." 

The Royal Australian Navy is seeking to acquire at least eight nuclear-powered submarines to replace the retiring conventionally powered Collins-class boats.

It will be the largest defence acquisition in Australia's history.

Experts have speculated about five boat options: the US Virginia-class; the British Astute-class; a hybrid based on the UK boat with a US weapons system; a newly developed US boat, the SSN (X); or a new British boat, the SSNR.

The fifth British Astute-class boat, HMS Anson, embarked on its inaugural voyage last month, with two more under construction.

But work is under way in the UK to design the Astute-class's replacement, the SSNR, which will notably have a vertical launch system allowing it to carry new missile types.

The US Navy has been rolling out Virginia-class boats since 1998 but is aiming to procure the SSN (X) in the mid-2030s as its successor.