The US Navy has awarded construction contracts to Lockheed Martin and Austal to build additional littoral combat ships (LCS).
Austal USA has received $691m in funding for the construction of LCS 22 and LCS 24, which brings the total contract value to A$3.1bn ($2.36bn).
In addition, the US Navy has included an option for the construction of an additional LCS 26, which can be exercised next year.
With this option, the total Independence-variant LCS constructed by Austal would be 13 ships, including 11 built by Austal and two by its subcontractor.
Austal CEO Andrew Bellamy said: "It is pleasing to see the navy's confidence in Austal's ability to produce these high-quality vessels."
Under the ten-vessel contract signed in 2010, Austal has seven LCS in various stages of construction at its shipyard in Mobile, Alabama, US.
Lockheed Martin was awarded a contract modification for one fully funded 2015 LCS valued at $362m, along with $79m in advanced procurement funding for a second ship.
This contract modification is for construction of LCS 21 and LCS 23, the 11th and 12th Freedom variant ships.
The vessels are being built by Marinette Marine Corporation, a Fincantieri company, with engineering support from naval architect Gibbs & Cox of Arlington.
The US Navy began the LCS programme in 2002 aimed to assemble a new class of up to 55 ships for multi-mission support.
Image: The US Navy's LCS 10, Gabrielle Giffords, with helicopter landing. Photo: courtesy of Austal.