Australia said the United Kingdom's British multinational aerospace, Defence and Information Security Company Systems would build a fleet of nuclear-powered submarines, a key step in fulfilling the landmark AUKUS security pact between Canberra, London and Washington.

Australia's Submarine Agency said BAE would produce the state-of-the-art vessels, which will be delivered from the early 2040s.

The agency didn’t reveal the exact number of submarines that would be built or financial details of the deal, but Australian Defence officials have said the country would get at least five of the SNN-AUKUS class subs at a cost of billions of dollars.

The first of the vessels are expected to be built in Britain, and later ones at a shipyard in Adelaide, South Australia.

The deal is reported to central an effort to overhaul Australia's military, as AUKUS members seek to check Chinese military expansion in the Asia-Pacific.

The subs would be quieter and stealthier than Australia's existing fleet, and capable of deploying over vast distances without surfacing, posing a potent threat to any foe.

Although the subs will not carry nuclear weapons, the technology underpinning their nuclear-propelled engines has been a tightly held secret between the United States and Britain for more than 60 years.