The National Nuclear Security Administration might lose political support in Congress if the New START nuclear arms control treaty with Russia lapses, the immediate past head of the semi-autonomous nuclear weapons agency said Wednesday.

About 80% of lawmakers on Capitol Hill, retired Air Force Lt. Gen. Frank Klotz said in a webcast hosted by the nonprofit, disarmament advocating Arms Control Association, support both nuclear arms modernization, and international nuclear arms control. 

To support his case, Klotz repeated the oft-cited notion that Democrats and Republicans, in a Democratic-majority Senate nearly a decade ago, bartered New START ratification for a 30-year, $1-trillion round of nuclear weapons modernization.

“Were we to withdraw, or allow New START to expire without replacement, I think that consensus would be in jeopardy,” Klotz said. “ I think it would seriously undermine the political support, the broad political support, which has been there for both the U.S. military’s nuclear modernization program as well as that of the Department of Energy and the National Nuclear Security Administration (NNSA).”

New START is set to expire in February, unless the White House and the Kremlin extend the deal for another five years beyond that. The treaty limits the U.S. and Russia to each deploying no more than 1,550 warheads across 700 intercontinental ballistic missiles, submarine-launched ballistic missiles, and heavy bombers.

The Trump administration has said it prefers a trilateral arms control treaty to replace New START: one that also constrains China’s nuclear arsenal, and places limits on Russian tactical nuclear weapons: relatively lower-yield weapons, of which Moscow has many more than the U.S., by far.

Those who support New START say there is plenty of time to negotiate such a treaty, once New START is extended. Some supporters accuse the White House of using the notion of a broader treaty as a John Rambo ploy — an impossible gambit meant to fail, and to key the White House’s real objective of walking away from any treaty that constrains U.S. arms. 

New START went into force in 2011, in a different political environment from today’s. Last year, Democrats who controlled the House were unable to win many firm concessions on nuclear arms, and were totally unable to stop the Trump administration’s low-yield warhead supplement to the Obama administration’s modernization program.

Should Trump win reelection and Republicans maintain even their razor-thin margin in the Senate, Senate Democrats would remain the chief bulwark against expanding the U.S. nuclear triad beyond New START limits — and to do it, they would have to be willing, at last move, to filibuster the annual National Defense Authorization Act, plus defense appropriation acts and energy and water appropriation acts.

“I wouldn’t just assume that this is automatically bipartisan,”Adm. Mike Mullen, former chairman of the Joint Chiefs of Staff, said on Wednesday’s webcast. “I’d want to test that pretty hard. It wouldn’t be as bipartisan as it was 10 years ago.”

On the other hand, former Vice President Joe Biden, the presumptive Democratic nominee for President, has said he would extend New START. With inauguration day only two weeks before the lapse of the treaty, there is, legally speaking, time for a prospective Biden administration to extend the deal. 

“None of us should forget, there’s an election in November,” Mullen said.