The Air Force said Tuesday it chose Northrop Grumman Corp., maker of the B-2 stealth bomber, to build its next-generation bomber, a highly classified, $80 billion project designed to replace the aging bomber fleet with an information-age aircraft that eventually may be capable of flying without a pilot aboard.

The loser of the high-stakes bidding contest was a team formed by Boeing Co. and Lockheed Martin Corp.

"The long-range strike bomber will support America's defense strategy by forming the backbone of the Air Force's future strike and deterrent capabilities," Defense Secretary Ash Carter said at a Pentagon news conference.

Carter said the new bomber will meet the nation's long-range strike aircraft needs for the next 50 years.

Wes Bush, chairman and chief executive of Falls Church, Virginia-based Northrop Grumman, said in a brief statement that his company will deliver on its promise to build a highly capable, affordable aircraft.

"Our team has the resources in place to execute this important program, and we're ready to get to work," Bush said.

The announcement marks an important step in the Pentagon's broader plan to modernize the entire nuclear force — missile-toting submarines, land-based intercontinental ballistic missiles and long-range bombers. The Congressional Budget Office estimates the cost at $348 billion over 10 years, and others have said it could approach $1 trillion over 30 years.

The Navy is committed to building a new fleet of 12 nuclear ballistic missile submarines to replace its 14 Trident submarines, and the Air Force is preparing to launch a program to build a modernized fleet of land-based ICBMs to replace its Minuteman 2 force. It's unclear, however, how the Navy and Air Force will manage this in an era of shrinking budgets.

Daryl Kimball, executive director of the Arms Control Association, said the administration is overreaching by investing so heavily in all three elements of the nuclear force.

"We believe the administration's redundant, all-of-the-above approach to rebuilding all of the major U.S. nuclear weapons delivery systems at levels beyond realistic deterrence requirements is unsustainable and will deplete resources from higher national security priorities," Kimball said.

The new bomber is a high Air Force priority because the oldest ones in its fleet — the venerable B-52s — have far outlived their expected service life and even the newest — the B-2 stealth bombers — having been flying for more than two decades. A third bomber, the B-1, is used heavily for conventional strikes, but no longer is certified for nuclear missions.

The Air Force said it will buy 100 of the new bombers at a newly calculated average cost of $564 million each. The Northrop Grumman contract awarded Tuesday is for an initial set of 21 planes, plus $23.5 billion in engineering and development costs. The estimated total cost to develop and purchase the full fleet would be $80 billion.

The Air Force said it has not picked a name or number designation for the new bomber. Some have dubbed it "B-3," since it follows the B-2, which entered service in the late 1980s.

Industry news reports say that while the new plane's specific capabilities are highly secret, it likely will be equipped with high-tech communications gear and other electronics that would allow it to perform a variety of missions, not just dropping bombs.

For the defense companies who sought the contract, the stakes were high. Boeing has built most of the Air Force's bombers, including the B-52. And it collaborated with Lockheed Martin on the F-22 stealth fighter. Northrop Grumman built the B-2 bomber fleet, which was originally planned to include 132 planes but was scaled back to 21 at the end of the Cold War.

Although construction site details weren't announced, California may benefit. Much of the plane's assembly could occur in the Southern California desert community of Palmdale, home of Air Force Plant 42, a military industrial park leased to aerospace contractors where the B-1 and B-2 bombers were built.

Northrop Grumman said last year it could create 1,500 new jobs in Palmdale under the bomber contract. The contract "means thousands of jobs will be coming to California, and that's great news," California state Assembly Speaker Toni G. Atkins said Tuesday.

Loren Thompson, a vocal advocate of the new bomber program, says it is a key part of modernizing the military at a time of increased U.S. focus on China's growing might.

"The simple truth is that if the United States does not revitalize its dwindling fleet of heavy bombers, it probably cannot prevail in a war against China," Thompson wrote earlier this month, citing what he called China's increasingly dense and agile air defenses. He heads the Lexington Institute, which receives funding from major defense contractors.

The Obama administration has justified its support for a new long-range bomber by calling it vital to retaining U.S. military predominance. In January, shortly before he left office, then-Defense Secretary Chuck Hagel visited a bomber base in Missouri to underscore his argument that a new bomber would help deter war and preserve the U.S. military's global reach.

Critics, however, question whether all three "legs" of the U.S. nuclear triad — bombers, subs and land-based missiles — are necessary in the long run. Each of the three has operated well beyond its intended life span, presenting an enormous challenge for the Pentagon at a time when it says budget pressures require it to scale back conventional forces.

The Pentagon also wants to buy a new air-launched nuclear-armed cruise missile at an estimated cost of $15 billion to $20 billion. That project has gained little public notice, although a former defense secretary, William Perry, drew attention inside the Pentagon earlier this month when he argued publicly that cruise missiles are a "uniquely destabilizing type of weapon" because they can be launched without warning and come in both nuclear and conventional variants.