The vessels -- the LCS Little Rock and LCS Sioux City -- will each be fitted out with two Rolls-Royce MT30 gas turbines, which will power four large Mk1 waterjets, providing the capability for the ships to reach speeds of more than 40 knots.
The LCS Milwaukee and the LCS Detroit, which are under construction, will feature the power systems under an earlier order. The USS Freedom and the USS Fort Worth, which is due to complete trials this spring, are also powered by Rolls-Royce.
"This order builds on the success of the Rolls-Royce-powered Littoral Combat Ships to date and we're delighted that we will also power the Little Rock and the Sioux City, said Andrew Marsh, Rolls-Royce, president-Naval.
"We have worked closely with Lockheed Martin, the U.S. Navy and other partners during the LCS program, using our extensive experience to further develop these highly advanced ships. The combination of the MT30 gas turbine and our latest waterjet technology will ensure these ships are at the cutting edge of global naval capability."