Australia unveiled on Sunday AU$3.9 billion ($2.8 billion) in spending as a "down payment" on a new facility that will build nuclear submarines under the tripartite AUKUS security pact with Britain and the United States.

"Investing in the Submarine Construction Yard at Osborne is critical to delivering Australia's conventionally-armed, nuclear-powered submarines," Prime Minister Anthony Albanese said in a statement.

The AUKUS pact aims to arm Australia with a fleet of cutting-edge submarines from the United States and would provide for cooperation in developing an array of warfare technologies.