The U.S. Missile Defense Agency has awarded Tucson-based Raytheon Missile Systems a $350 million contract add-on for the procurement of Standard Missile-3 Block IB interceptors.

The additional funding increases the fiscal 2014 contract award to $506 million for the procurement of 44 Standard Missile-3 Block IB guided missiles.

The SM-3 Block IB is designed to destroy incoming short-, medium-, and intermediate-range ballistic missile threats as part of the nation’s sea-based missile defense system. The Block IB had a successful series of tests last year and is ready for full-rate production, Raytheon said.

Mitch Stevison, Raytheon Missile Systems’ Standard Missile-3 program director, said in prepared remarks that the company is continuing to deliver the final SM-3 Block IAs on order, while increasing its production rates of the SM-3 Block IBs.