The U.S. Missile Defense Agency will purchase 20 additional Lot 8 interceptors under a contract modification with Lockheed Martin.

The modification, valued at $198.7 million, will support the Missile Defense Agency's Terminal High Altitude Area Defense project, bringing the cumulative value of the contract up to $822 million.

THAAD is designed to protect population and high-value infrastructures from short and medium-range ballistic missile attacks, using interceptors to engage incoming targets. The system is capable of intercepting missiles inside and outside of the atmosphere.

Work on the contract will be performed at several locations in Texas, Alabama, and Arkansas, and is expected to be complete by September 2019.

Lockheed Martin announced they received a $528 million contract to produce and deliver THAAD missile systems in early January 2016. The systems were to be used by the U.S. Army to enhance its ballistic missile interception capabilities.