The Air Force plans to award a contract sometime between July and September of 2020 to build the U.S.’ next nuclear-tipped, intercontinental ballistic missile, the service said Tuesday. 

The Air Force plans to buy more than 600 Ground Based Strategic Deterrent (GBSD) missiles, about 400 of which will go into silos starting in 2028 or so to replace the aging, Boeing-built Minuteman III fleet. Either Boeing Co. [BA] or Northrop Grumman [NOC] will design GBSD. 

The planned GBSD Engineering and Manufacturing Development contract will have options for five batches, or production lots, of missiles. That will include manufacturing and deploying the missile.

Boeing and Northrop Grumman are in the final year of a competition, under three-year Pentagon contracts awarded in 2017 and respectively worth about $350 million and $330 million, to design the next-generation missile. The Air Force estimates it will spend between roughly $85 billion and $100 billion to procure GBSD, according to the Washington-based non-profit Arms Control Association.

GBSD will carry W87-1 warheads provided by the Department of Energy’s National Nuclear Security Administration (NNSA). The W87-1 will be a new manufacture of an old design: the W87 warhead used on Minuteman III. Minuteman III also uses W78 warheads, but the Pentagon plans to replace these with W87-1 on GBSD. 

W87-1 will cost between $10 billion and $15 billion over the 20 years ending around 2040, NNSA estimated last year. In addition, NNSA plans to spend $30 billion over several decades beginning this year on specialized plutonium-manufacturing infrastructure needed to produce the pits, or triggers, for W87-1 warheads.

NNSA plans to begin producing W87-1 pits at the Los Alamos National Laboratory beginning in 2024. The civilian agency then plans to upgrade pit facilities at Los Alamos and build a new pit plant in South Carolina to ramp up production of W87-1 cores to 80 a year by 2030. However, multiple internal NNSA studies concluded the agency probably will not hit its target throughput by its target date.

House Democrats, meanwhile, want to slow down the GBSD program. In defense authorization and spending bills passed this summer, the lower-chamber’s minority proposed funding cuts for both the Pentagon and NNSA side of the program.

The House-passed bills would authorize and appropriate $490 million for GBSD in fiscal 2020: nearly 15% less than the $570 million the White House requested. For W87-1, the bills would provide under $55 million for 2020, which is less than half of what the White House requested. The measure would fund NNSA’s pit-funding, Plutonium Sustainment account at about $470 million: nearly 35% below the request.

House Democrats are essentially alone on the Hill in their desire to slow GBSD.

While the Senate has yet to write any appropriations bills, the upper chamber authorized $590 million for GBSD in fiscal year 2020 in a National Defense Authorization Act that cruised through the Senate with plenty of support from Democrats. The Senate also authorized the requested 2020 funding for NNSA’s plutonium programs.