WASHINGTON — A top defense appropriator wants to waive Congress’ use-it-or-lose-it rules to let the Pentagon use its fiscal 2018 funding boost in next year’s budget, too, arguing there isn’t enough time to efficiently spend the money.

Rep. Kay Granger, chairwoman of the House Appropriations Defense Subcommittee, told Defense News on Wednesday that Congress must act to fix an “artificial deadline,” or the military risks losing funds afforded by a new budget deal.

“I couldn’t be more proud of what the Congress approved for defense, but we certainly don’t want to waste that and we don’t want to lose it,” said Granger, R-Texas.

Still, the path for such a measure is unclear, as Democrats are signaling they will drive a hard bargain in ongoing negotiations on how to spend the added $80 billion provided to defense by the recent budget deal.

Because Congress has yet to reach a final budget agreement for FY18, which began Oct. 1, 2017, the military has been operating at 2017 spending levels. Appropriators are expected to propose an omnibus spending bill before the latest funding patch expires March 23.

Without congressional action, the military would have five months or less to spend the big bump afforded by the deal on budget top lines, which gives the Department of Defense nearly $700 billion for FY18 and $716 billion for FY19.

Under current rules, money not spent by government agencies before the end of the fiscal year goes back to the Treasury Department.

Defense Secretary Jim Mattis has railed against Congress’ reliance on stopgap measures, or continuing resolutions, to fund the government, saying in June congressional testimony that funding instability has “blocked new programs, prevented service growth, stalled industry initiative and placed troops at greater risk.”

To soften the impact, lawmakers have since approached Pentagon leaders with the idea of stretching 2018 funds and more recently requested a DoD outline of what it would like extra authority to do. The lawmakers were awaiting a reply, as of Wednesday.

Granger wants the DoD to make the case for flexibility in other categories, but she anticipates the authority ultimately will be narrow, with increased oversight.

Still, the Senate’s No. 2 Democrat and ranking member on the Senate Appropriations Defense Subcommittee, Sen. Dick Durbin, expressed skepticism Wednesday.

“If there is a good case to be made for some flexibility around the margins to better support the women and men of the armed forces and their families, that’s a reasonable discussion to have,” said Durbin, of Illinois.

But Durbin pushed back on another proposal of Granger’s — a $28.6 billion fund for the Pentagon that could be used at Mattis’ discretion to give the military the ability to rebuild forces as “slush funds, a proposal that will not fly.” Durbin also pointed to a Defense Logistics Agency audit that found $800 million in spending that could not be justified.

“I’m willing to hear Secretary Mattis out on any proposals he has for the spending increases, but I will want to know how we appropriators make sure that every dollar will be well-accounted for,” Durbin said.

According to Granger, the priority for funding flexibility is with operations and maintenance funding, which must be obligated within one year. O&M also covers military readiness, the center of pro-defense lawmakers’ successful argument for the added funding.

It’s an open question, what the legislative vehicle will be, though it’s likely be the omnibus or a standalone bill. Either way, Granger wants to vet the idea with colleagues of both parties and act quickly.

Both House Armed Services Committee Chairman Mac Thornberry, R-Texas, and the Senate Armed Services Committee’s No. 2 Republican, Sen. Jim Inhofe, R-Okla., have publicly signaled support, as have military leaders.

Stretching funds from one year to the next is not unprecedented, but appropriators are typically reluctant to do so. Bob Hale, a DoD comptroller under President Barack Obama, said he pressed, to no avail, for 5 percent carryover authority to avoid inefficient, year-end spending sprees that plague the department.

“They paint the conference room or buy new furniture because they think if they don’t spend it, they wont get it the following year,” said Hale, now a senior adviser to Booz Allen Hamilton. “If you gave them 5 to 10 percent carryover, they might wait and decide to spend that on training.”

The Heritage Foundation, an influential conservative think tank, has come out in favor of limited carryover authority of up to 5 percent for the DoD’s operating budget.

“The time crunch created by continuing resolutions and the use-it-or-lose-it system can force the DoD into suboptimal decision-making, like focusing on what it can buy ‘right now’ instead of making the acquisitions the military actually needs,” Fred Bartels, of the Heritage Foundation, said Wednesday. “Congress should try giving DoD substantial carryover authority and focus its oversight on what the department actually does with that increased discretion.”

For her part, Granger is banking that Capitol Hill’s general goodwill toward defense will carry the day.

“It needs to be explained, but I think it will have support because the defense bill had so much support,” Granger said of her forthcoming proposal. “If we go back around and say, ‘[For] all this support we gave them, some of that would be lost if don’t do this,’ I think people will be very supportive.”