The US State Department has approved the sale of some 220 cruise missiles to Australia in a deal valued at $895m.
The proposed sale, which requires sign-off from Congress, includes Tomahawk missiles and technical support.
The missiles will be used by the Virginia-class submarines Australia will acquire from the US under the Aukus defence pact.
Australian Defence Minister Richard Marles said the missiles would provide “a really important capability”.
The deal would enable the country “to reach out beyond our shores further and that’s ultimately how we are able to keep Australia safe” the minister told the Australian Broadcasting Corporation (ABC).
The missiles could be initially deployed on Australia’s Hobart-class destroyers before the first Aukus submarines are delivered, ABC reported.
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”.
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”.
A number of senior Australian political figures have also voiced concerns.
Former prime minister Paul Keating attacked Aukus as “worst international decision” by an Australian Labor Party government since World War I, which would send the country down “a dangerous path”.
Another former leader, Malcolm Turnbull, also questioned whether the UK was a feasible long-term partner in the treaty given “fundamental existential problems” with its economy.
“You’ve got to ask yourself whether Britain is going to be able to sustain investment in its navy and its military in the years ahead,” Mr Turnbull said in a speech at the Defence Club in Canberra.