The Pentagon said the sale would "improve Australia's capability to interoperate with US maritime forces and other allied forces as well as its ability to contribute to missions of mutual interest".
US, UK and Australia agree on nuclear submarine project
Is conflict between West and China getting closer?
The Aukus deal, unveiled on Monday in San Diego, binds together Australia, the UK and the US in a far-reaching defence alliance which will confront Chinese military expansion in the region.
China has condemned the pact as "risking a new arms race and nuclear proliferation".