"We intend to build these submarines in Adelaide, Australia, in close cooperation with the United States and the United Kingdom," he said in a video conference with US President Joe Biden and British Prime Minister Boris Johnson.

The submarines are not intended to carry nuclear weapons, the leaders said, as they announced a landmark security pact dubbed AUKUS.

Morrison said the nations would "work together to seek to determine the best way forward to achieve this" over the next 18 months.

"This will include an intense examination of what we need to do to exercise our nuclear stewardship responsibilities here in Australia," he said.

Nuclear power has been highly controversial in Australia and Canberra formally banned the use of nuclear energy in 1998, though the country has rich deposits of uranium.

The announcement comes as Australia has been boosting defense spending as it looks to a rapidly rising and more assertive China.

Morrison said the new trilateral partnership was forged in a "more complex" Indo-Pacific region and would help to "meet these challenges".

It was not immediately clear what the announcement meant for a troubled Aus$90 billion (US$66 billion) submarine deal with France to replace Australia's ageing fleet of Collins class submarines.

The deal with France's Naval Group to build 12 state-of-the-art Attack Class subs is years behind schedule, well over budget and has become tangled up in Australian domestic politics.

As recently as June, President Emmanuel Macron promised "full and complete" commitment to the deal. But a top Australian defense official said around the same time that Australia was actively considering alternatives.

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NAVAL GROUP