Raytheon has received a $68 million contract modification for continued Standard Missile-3 Block IIA engineering.

The modification, awarded for the U.S. Missile Defense Agency, brings the total cumulative value of the initial contract to $1.95 billion, and falls under Phase II of the agreement. Congress was first notified of the procurement in February 2016.

Work on the contract will be performed at Raytheon's facility in Tucson, Ariz. The U.S. Department of Defense expects Phase II to be completed by the end of September 2018. The Missile Defense Agency in Dahlgren, Va., is listed as the contracting activity.

The Standard Missile-3, or SM-3, is a defensive interceptor used by the U.S. Navy to engage short- to intermediate-range ballistic threats. The SM-3 Block IIA variant covered by Raytheon's recent contract modification is being developed in collaboration with the government of Japan, and features larger rocket motors in addition to larger kinetic warheads.

Phase II of the program began in 2014. Phase III, which includes testing, is set to begin in 2018.