WASHINGTON — If the Defense Department is forced to get rid of its intercontinental ballistic missiles, it will have to move its bombers to alert status to pick up the slack, the head of U.S. Strategic Command said Tuesday.

The U.S. military maintains a “nuclear triad” of ICBMs, bombers and ballistic missile submarines meant to deter nuclear-armed adversaries from attacking the nation, as the United States could respond with a subsequent attack even if a portion of its nuclear arsenal was wiped out.

“The basic design criteria of the triad is that you cannot allow a failure of any one leg of the triad to prevent everything the president has ordered you to do,” said Adm. Charles Richard during a Senate Armed Services Committee hearing.

When bombers are on alert status, they sit parked on the runway, ready to take off with nuclear weapons loaded. Richard argued that, because the United States removed its bombers from alert status after the end of the Cold War, it essentially functions with only its Minuteman III ICBMs and Columbia-class ballistic missile submarines prepared to take on the nuclear mission at a moment’s notice.

“What is not often recognized is that we do not have a triad from day to day. ... Day to day, what you have is basically a dyad,” Richard said.

“If you don’t have intercontinental ballistic missiles ... you are completely dependent on the submarine leg,” he said. “I’ve already told the secretary of defense that under those conditions, I would request to re-alert the bombers.”

The Biden administration is expected to assess the nation’s nuclear arsenal as part of a wide-ranging nuclear posture review. Richard’s comments come as the ICBM leg of the triad incurs increased scrutiny by left-leaning lawmakers and arms control advocates who have argued that the United States can still deter its adversaries with only its bombers and submarines.

That debate could leave the Air Force’s Minuteman III replacement vulnerable to deferral or outright cancellation. The Defense Department expects acquisition costs for the Ground Based Strategic Deterrent program, currently under development by Northrop Grumman, to amount to more than $95 billion.

Richard has repeatedly spoken against delaying the GBSD program, saying during the SASC hearing on Tuesday that he could not deter China and Russia with the “leftovers of the Cold War” and arguing that the Minuteman III was too old to be life-extended.

“I need weapon systems that will ultimately work and actually make it to the target,” he said. “What they are doing to keep the [Minuteman III] functioning — remember, that is a ’70s-era weapon system that I’m going to employ against 2030-level threats. We are down to two of a particular type of switch that is required to go in the launch control centers. Nobody knows how to make it anymore. It’s obsolete, it’s not worth [it for] a company to put their effort into [making] that.”

In the hypothetical case that the United States did decommission its ICBMS, Richard did not lay out which of its bombers would be put on alert status.

The U.S. Air Force retains two nuclear-capable bombers — the Boeing B-52 Stratofortress and Northrop B-2 Spirit — as the B-1 Lancer was converted to conduct conventional missions only as part of the Strategic Arms Reduction Treaty.

The 1950s-era B-52 is capable of launching the nuclear version of the Air Launched Cruise Missile, while the stealthy B-2 can drop nuclear gravity bombs including the B61 and B83. Both bombers will be able to use the ALCM’s replacement, the Long Range Stand Off (LRSO) weapon currently under development by Raytheon.

In 2017, Defense One reported that the Air Force was taking steps to get its B-52s ready to go back on alert status, due in part to what was seen as a rising nuclear threat from North Korea. The order, which would have stemmed from STRATCOM or U.S. Northern Command, was ultimately never given.