As the prime contractor, Austal currently has contracts to build the first three JHSVs as part of a 10-vessel program valued at up to AU$2 billion.
The latest award funds the acquisition of long lead-time material for JHSV 4 and 5.
"This award signifies the US Navy's continued commitment to the JHSV program and confidence in Austal's ability to reliably deliver the predecessor ships on time and budget," Austal USA President and COO Joe Rella said.
"The long lead-time material contract award also ensures employment continuity for our US workforce."
Austal was awarded the initial contract to design and build the first 103-metre JHSV in November 2008, with contracts for an additional two vessels awarded in January this year.
Options for the remaining seven vessels are expected to be awarded between FY10 and FY13.
Similar to the Austal-built "WestPac Express" operated by the US Marines for the past eight years, the JHSV will be capable of transporting troops and their equipment, supporting humanitarian relief efforts, and reaching speeds in excess of 35 knots fully loaded.
The vessels will be a joint-use platform operated by both the United States Army and Navy.
Construction of JHSV 1 "Spearhead" is currently underway (pictured) at Austal's US facility in Mobile, Alabama, with a keel laying ceremony to be held shortly.
JHSV 2 is scheduled to commence construction in September this year, with JHSV 3 to commence in mid-2011.
Long lead-time material for JHSV 4 and 5 will include main propulsion engines, water jets, reduction gears and other major equipment items.
General Dynamics Advanced Information Systems is the platform mission systems engineering agent responsible for the design, integration and test of the ship's electronic mission systems, including an open architecture computing infrastructure, internal and external communications, electronic navigation, aviation and armament systems.