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.