Boeing and Northrop Grumman both won contracts Monday for the next phase of the Air Force's Ground-Based Strategic Deterrent program to replace its Minuteman III missiles, the Defense Department announced.

The development leaves Lockheed Martin out of the competition to replace the intercontinental ballistic missile, which is the land-based leg of the nation's nuclear triad.

Boeing received a $349 million contract, while Northrop's was for $328 million. The cash covers "technology maturation and risk reduction" for the program and work will be completed by Aug. 20, 2020, the Pentagon said. After this phase, the Air Force will choose a single contractor to build the missiles.

"We look forward to the opportunity to provide the nation with a modern strategic deterrent system that is secure, resilient and affordable," said Wes Bush, Northrop's chairman, chief executive officer and president. "As a trusted partner and technical integrator for the Air Force's ICBM systems for more than 60 years, we are proud to continue our work to protect and defend our nation through its strategic deterrent capabilities."

In a statement, Boeing said "the decision reflects confidence in our design solution.

"We are honored to continue our long-standing partnership with the Air Force to provide an affordable, low-risk intercontinental ballistic missile (ICBM) system solution," spokesperson Jerry Drelling said in a statement. "Boeing's GBSD concept will put the Air Force on track to field a new ICBM in the next decade, an ICBM with unmatched strategic deterrence capability."

Boeing also touted the fact that its manufactured the Minuteman missile.

"Since the first Minuteman launch in 1961, the U.S. Air Force has relied on our technologies for a safe, secure and reliable ICBM force," said Frank McCall, Boeing director of Strategic Deterrence Systems and GBSD program manager. "As the Air Force prepares to replace the Minuteman III, we will once again answer the call by drawing on the best of Boeing to deliver the capability, flexibility and affordability the mission requires."

The Minuteman III has garnered attention amid North Korea's nuclear missile development. Each time the Air Force tests one of its unarmed Minuteman III missiles, most recently this month, it's viewed as a message to Pyongyang, even though Air Force officials point out that the tests are planned years in advance.