(CNN)The top US military official who runs the American nuclear arsenal warned that China and Russia are modernizing their nuclear weapons and capabilities faster than the US, saying during a congressional hearing on Tuesday that if it does not start investing more in nuclear defense and infrastructure, the US will be "at risk of losing credibility in the eyes of our adversaries."
Russia is "aggressively engaged" in "conventional nuclear capability development and modernization, and are now roughly 80% complete while we are at zero," saId Adm. Charles Richard, the head of US Strategic Command, which oversees the US nuclear arsenal.
"It is easier to describe what they are not modernizing -- nothing -- than what they are, which is pretty much everything," Richard said.
Richard said China is modernizing its nuclear capabilities so quickly that he "can't get through a week right now without finding out something we didn't know about China."
While China's nuclear stockpile is vastly smaller than the United States' and Russia's nuclear arsenals, it is undergoing an "unprecedented expansion," Richard said in his opening testimony.
Russia and the US are limited to some 1,550 nuclear warheads on deployed intercontinental ballistic missiles, deployed submarine-launched ballistic missiles and deployed heavy bombers equipped for nuclear armaments, according to the latest START treaty.
It is estimated that China has only about 320 warheads, according to the Stockholm International Peace Research Institute.
The Biden administration is currently carrying out a nuclear posture review, which is examining the total amount of money invested in the nuclear modernization program. The purpose of the review is to "reduce the goal of nuclear weapons in our defense strategy," Sen. Elizabeth Warren, a Massachusetts Democrat, said during the hearing.
"I agree with that goal, and I think it is incompatible with that staggeringly high level of spending. Every administration makes strategic decisions about our force structure and modernization, and when it comes to nuclear weapons, those decisions carry tremendous weight," Warren said.
Operations, interim upgrades and full modernization of the US nuclear weapons program could cost $1.2 trillion, according to an October 2017 report from the Congressional Budget Office.
Two weeks ago, Richard gave an order at US Strategic Command requiring any brief discussing potential threats from China or discussing China in general that is more than a month old be updated because "it's probably out of date," he said during the hearing.
Richard warned China is making rapid advances
About a week ago, Richard learned that China now has more fast-breeder nuclear reactors than it previously did, an example of "how rapidly China is changing, or at least how rapidly we are figuring it out," he said.
"With a fast-breeder reactor you now have a very large source of weapons-grade plutonium available to you," Richard said. "That will change the upper bounds of what China could choose to do if they wanted to in terms of further expansion of their nuclear capabilities."
A fast-breeder reactor makes more fissile material than it consumes. The revelation that China has more fast-breeder reactors means it is potentially developing more nuclear material that can be used for nuclear weapons.
Richard also warned that China has moved a portion of its nuclear forces to a "launch on warning" posture and is "adopting a limited 'high alert duty' strategy," meaning it could be ready to launch a retaliatory strike as soon as its sensors detect an incoming threat. It is US policy to ensure it knows the trajectory of a missile if one is detected and to try to assess if it's nuclear before striking.
The information Richard referred to in the hearing regarding China's nuclear weapons and their capabilities was gathered by the intelligence community, a spokesperson for US Strategic Command said.
Russia, on the other hand, is "across the board operating new equipment," Richard said when discussing the country's nuclear weapons and capabilities.
"They are on the second generation of a new ballistic missile submarine. They have a new ballistic missile for that. It's quite capable," Richard said. "They have a very impressive solid-fueled intercontinental ballistic missile, brand new.
"They have new road mobile missiles. They have up-gunned their bombers. They have new weapons off their bombers."
Richard warned that while the US has an "adequate missile defense," right now, "we do need to make sure we pace it into the future against the threats that we're seeing."
"Without the recapitalization of the existing weapons we risk obsolescence and irrelevance, and we could reach a point where no amount of money will adequately mitigate the operational risks we'll be facing," he said.
