The U.S. Missile Defense Agency has awarded Tucson-based Raytheon Missile Systems a $241 million contract modification for continued engineering design and development work on the Standard Missile-3 Block IIA system.

The SM-3 Block IIA is a join development effort between the U.S. and Japan and a key part of phase three of the Obama administration's Phased Adaptive Approach to missile defense.

The SM-3 Block IIA's larger rocket motors and advanced kinetic warhead will allow for a greater area defended against ballistic missiles, the company said.

SM-3 is being developed as part of the Missile Defense Agency's sea-based Aegis Ballistic Missile Defense System. The missiles are deployed on Aegis cruisers and destroyers to defend against short- to intermediate-range ballistic missile threats in the midcourse phase of flight.