Military officials warned on Friday that the National Guard will be forced to make drastic cuts starting next month if Congress does not reimburse expenses incurred while defending the U.S. Capitol after the Jan. 6 insurrection.

Training exercises and drill weekends will probably be canceled and thousands of full-time employees put on furlough, Guard leaders told reporters. Aircraft will be grounded and maintenance delayed, they warned. In effect, any account that Guard units drained to float the more than $520 million security mission will be a potential area for cuts, risking their ability to respond to the next domestic emergency that arises.

“This will have an effect across the 50 states and the District of Columbia,” said Brig. Gen. Craig Strong, a deputy director of programming with the National Guard Bureau. “There is an effect on their readiness accounts to train and equip the soldiers and airmen. . . . This impact is definitely a national situation.”

The mobilization of more than 25,000 Guard troops to protect the Capitol lasted nearly five months. Both Democrats and Republicans agree that the costs they incurred are important to repay.

But the effort to settle accounts with the National Guard and other federal agencies that responded when supporters of President Donald Trump attacked the building has become mired in a broader debate about how to pay for enhanced security moving forward.

This spring, the House narrowly approved a $1.9 billion measure to cover the mobilization and pay for security improvements to the Capitol complex, including additional screening checkpoints, hardened windows and doors, and a new quick reaction force to be housed with the D.C. Guard. But Republicans opposed spending so much on upgrades before Congress takes additional steps to determine and correct what went wrong.

The House recently created a select committee to look into the events of Jan. 6, with nearly all Republicans opposing. House Speaker Nancy Pelosi (D-Calif.) decided to set up the panel after the Senate killed a bipartisan effort to appoint an independent commission of outside experts to look into the Capitol uprising. The select committee holds its first public hearing July 27.

In recent months, a series of experts — including Capitol Police Inspector General Michael A. Bolton and retired Lt. Gen. Russel Honore, who led a task force examining security at the Capitol — have identified a number of shortcomings with campus security, particularly regarding training and intelligence analysis. A recent bipartisan report from the Senate Rules and Administration, and Homeland Security and Governmental Affairs committees echoed many of those findings.

The House bill would have paid for improvements to those areas as well. But the debate is bottlenecked in the Senate, where Appropriations Committee Chairman Patrick J. Leahy (D-Vt.) this week released an more comprehensive proposal to pay for security improvements and “other pressing matters.”

Leahy’s $3.7 billion bill couples a number of Capitol security initiatives with significant investments to offset the effects of the coronavirus pandemic on federal government operations. It also seeks to help refugees fleeing Afghanistan and fund special immigrant visas to allow Afghans who helped the U.S. military come to the United States.

The bill “addresses all of the needs arising from the tragic events of January 6th and the global pandemic,” Leahy said in a statement defending his legislation. “We must act in a comprehensive way . . . we only have one shot at this, and we have a responsibility to get it right.”

But in a sign of the political discord surrounding the matter, the committee’s top Republican, Sen. Richard C. Shelby (Ala.), released an emergency supplemental measure of his own, priced at $633 million — to cover just the debts owed to the National Guard and the Capitol Police.

“The clock is ticking. Let’s pass what we all agree on,” Shelby said in a statement accompanying his proposal.

On Friday, National Guard leaders declined to comment on any of the more contentious issues slowing progress on the supplemental. But they bemoaned the fact that repaying debts owed to the National Guard is being caught up in a greater budget battle.

“What’s most important is that Congress really addresses the issue with the budget shortfall,” said Maj. Gen. Richard R. Neely, head of the Illinois National Guard. “The National Guard was asked to come to a mission. . . . It’s important not to let this discussion get pulled into what’s the best security for the Capitol.”