Nuclear sub fleet won't sink ties with China, says PM

Anthony Albanese has shot down Chinese attacks on Australia's buy-up of nuclear-powered submarines, arguing the nation can boost its military might while improving relations with Beijing. 

It wasn't contradictory for Australia to invest in a fleet of the latest naval weaponry at the same time as building upon its relationships with other countries in the Indo-Pacific, the prime minister said.

"It's a consistent position, we need to ensure that Australia's defence assets are the best they can be," he told reporters in New Delhi.

"At the same time we need to build relationships. We're doing that throughout the Indo-Pacific ... we've improved our relationship with China in recent times as well."

Mr Albanese is expected to join US President Joe Biden and British leader Rishi Sunak in San Diego on Tuesday to announce how Australia intends to buy a fleet of nuclear-powered submarines under the AUKUS arrangement.

China's foreign ministry spokeswoman Mao Ning accused the AUKUS partnership of undermining the international non-proliferation of nuclear weapons agreement.

"We urge the US, the UK and Australia to abandon the Cold War mentality and zero-sum games, honour international obligations in good faith and do more things that are conducive to regional peace and stability," she said.

While details have not been confirmed, the AUKUS deal is expected to involve Australia acquiring up to five US Virginia-class submarines, with the remaining boats to combine a British design with US technology.

Defence Minister Richard Marles described it as the "biggest step forward in our military capability that we've had since the end of the Second World War".

Asked about the potential for a capability gap until the delivery of the nuclear-powered submarines, Mr Marles backed the existing conventionally powered Collins-class fleet, but said a more potent boat was needed in the next decade.

"There is nothing which gives any adversary a second thought more than a capable submarine, which is why it's so important that we're bringing to bear this capability in the future," he said.

Opposition Leader Peter Dutton said the impending announcement was a great outcome for the country.

"The Virginia-class is an established class, so you don't have the problems of a first-in-type, the new design, cost blowouts," he said.

"The acquisition of the Virginia-class is in our country's best interests and we strongly support it."

South Australian Premier Peter Malinauskas said he had been given the commitment his state would be building a nuclear submarine. 

"We all accept and understand that when it comes to a nuclear submarine there will be sharing of componentry between nations," he said.

"Sovereign capability is best derived from having a workforce that is capable of building nuclear submarines.

"We have the ability to deliver that here in South Australia."

Australian Strategic Policy Institute senior analyst Malcolm Davis said getting the Virginia class submarines would mean having a capability "much earlier than planned".

But he said there would be added cost in running two different types of submarine simultaneously.