WASHINGTON — Boeing has won a sole-source, $6.6 billion deal to build a new silo and 20 more ground-based interceptors (GBI) and to sustain the Ground-based Midcourse Defense (GMD) system from the U.S. Missile Defense Agency, according to a Jan. 31 Pentagon announcement.

The award is an undefinitized modification of a previous contract for development and sustainment of the GMD system — the primary homeland defense system against possible intercontinental ballistic missile attacks from North Korea and Iran.

If all options are exercised, the total contract could total $12.6 billion, which includes the previous contract amount of $6.1 billion.

Under the contract modification, the MDA “executes missile defeat and defense enhancements to complete the accelerated delivery of a new missile field with 20 additional silos and two additional silos in a previously constructed missiled field at Fort Greely, Alaska, and the procurement and deployment of 20 additional [GBIs],” the announcement states.

There are currently 44 GBIs installed in the United States, 40 at Fort Greely and four at Vandenberg Air Force Base, California. The 44th and final GBI — under the previous requirement — was put in place at Greely on Nov. 2.

As fear of missiles from North Korea and Iran reaching U.S. soil increase, the Pentagon, the White House and Congress have majorly boosted funding to build an increasingly robust system to defend the homeland against ICBM threats.

The Pentagon and the MDA had indicated in the fall of 2017 that it intended to build up the GMD system beyond 44 interceptors. In September, the Pentagon proposed reprogramming $136 million in fiscal 2017 to start raising the number of GBIs from 44 to 64 in a new Missile Field 4 at Fort Greely. The boost was part of a $416 million reprogramming request targeting missile defense needs.

And the White House submitted a supplemental budget request for FY18 in November 2017 that asked for further funding to increase the number of GBIs by 20 and to build an additional missile field at the Alaska base.

The conference report of the FY18 defense policy bill authorized the defense secretary — subject to what is appropriated — to increase the number of GBIs by up to 28. The conference report also required the defense secretary to develop a plan to increase the capacity, noting the currently available space in the missile fields could fit 104 GBIs.

The scope of work for Boeing’s new contract modification includes providing technical capabilities to “expand and improve” the missile defense system “to ensure defensive capabilities remain both relevant and current,” according to the contract announcement.

That would include boost vehicle development and integrating a redesigned kill vehicle, or RKV, with the boost vehicle.

The MDA is investing in an RKV for the Ground-based Midcourse Defense system that will increase the performance of the current exoatmospheric kill vehicle, or EKV, which has struggled in testing.

The EKV is a component of the Ground-based Midcourse Defense interceptors designed to destroy targets in high-speed collisions after separating from the booster rocket. The RKV is expected to deploy in the 2020 time frame.

The issues with the EKV have been resolved and the system has performed well in tests in recent years, including a challenging test in May 2017 where the system went up against an ICBM-class target and obliterated the threat.

Boeing must also provide GBI assets for labs and test events, as well as develop, integrate, test and deploy ground systems software builds to “address emerging threats;” acquire and emplace launch-support equipment; and expand systems testing, cybersecurity and performance-based logistics, according to the Defense Department announcement.

The period of performance for the contract is January 2018 through December 2023.

The announcement also notes that while Boeing will be the lead, the contract modification will be “performed by an industry team” including Orbital ATK, Northrop Grumman and Raytheon.

The sole-source contract is justified because Boeing is already the prime contractor for the GMD system and no other company has the capabilities to “satisfactorily” perform the services and deliveries without delays, according to the notice.

The Pentagon says it was able to obligate $213 million at the time of the contract award using FY17 and 2018 research, development, test and evaluation funds.