Progressives have recently found themselves in an unfamiliar position: in agreement with members of the hard-right House Freedom Caucus.

Some of the latter caucus’s members have recently called for re-examining the amount of money spent by the US military, echoing demands that progressives have issued for years. Although progressives are clear-eyed about their ideological differences with “America first” Republicans on foreign policy, they encourage a renewed debate over the Pentagon’s budget.

“The idea that effective American foreign policy requires this [level of spending], I think, is not only wrong,” said Matt Duss, a former foreign policy adviser to progressive senator Bernie Sanders, “it’s just absurd and unsustainable.”

The Freedom Caucus reportedly pushed for spending cuts as part of their negotiations with Kevin McCarthy, who offered concessions to fellow Republicans to secure the House speakership earlier this month. One of those concessions involved a promise to cap fiscal year 2024 discretionary spending at fiscal year 2022 levels, after Republicans expressed outrage over the $1.76tn omnibus funding bill that Joe Biden signed into law last month.

If such a fiscal policy were evenly applied to all federal agencies, the department of defense would see its budget cut by $75bn compared with this fiscal year.

That possibility has simultaneously sowed division among House Republicans and attracted the interest of progressives. They hope the latest dust-up over the Pentagon’s budget will spark what they consider to be an overdue conversation over US defense spending, which will hit a record high of $858bn this fiscal year.

Among House Republicans, the proposal to cut the Pentagon’s budget has won some support from far-right members who have embraced Donald Trump’s “America first” approach to foreign policy. Speaking to Fox News this month, Congressman Matt Gaetz, one of the Republican holdouts in the speakership battle, partly blamed the Pentagon’s large budget on America’s financial assistance to Ukraine amid its war against Russia.

“We can defend this country and project power more efficiently and more effectively than we do,” Gaetz said. “How about we start with Ukraine?”

McCarthy himself previously promised that Republicans would not provide a “blank check” to Ukraine if they won back the House. But aid to Ukraine has continued to win bipartisan support in Congress.

“I do not see that money getting taken away from us,” Biden’s national security adviser, Jake Sullivan, said earlier this month. “It is there. It is rock solid through nearly all or all of 2023.”

McCarthy has expressed openness to examining the Pentagon’s budget, but the proposal has stoked outrage among many of the more hawkish members of his conference. Republican congressman Tony Gonzales of Texas cited the potential cuts to explain his opposition to the House rules package, saying he thought the proposal was a “horrible idea”.

“How am I going to look at our allies in the eye and say, I need you to increase your defense budget, but yet America is going to decrease ours?” Gonzales told CBS News.

While a number of House Democrats have joined Gonzales in rejecting the idea of defense spending cuts, the idea of reconsidering the Pentagon’s budget has long held sway with progressives. When Biden called for an increase in funding for the defense department last year, leaders of the Congressional Progressive Caucus attacked the proposal as “simply unacceptable”. Progressive activists and their congressional allies note that the US military has a larger budget than the next nine largest militaries combined and urged lawmakers to reallocate some of that funding to other needs, such as healthcare or education.

“For far too long, we have blindly and excessively pumped money into the Pentagon, which – despite its massive budget – has yet to pass an audit,” said the progressive congresswoman Barbara Lee, who has long championed fiscal reform at the defense department. “Imagine what we could do with even a fraction of [the Pentagon’s funding]. We need to rethink our foreign policy priorities and invest in diplomacy first and defense second.”

Ro Khanna, a progressive congressman from California, said he would welcome a bipartisan conversation about the Pentagon’s budget, but he rejected Republicans’ efforts to tie spending cuts to the looming fight over the debt ceiling. The US hit its debt limit this month, and the treasury secretary, Janet Yellen, has warned that the government is at risk of defaulting this summer if Congress does not increase its borrowing capacity – a move that would have catastrophic effects on the US economy. Democrats fear that House Republicans will attempt to extract concessions on government spending in exchange for helping to raise the debt ceiling.

“I do not support any debate on spending demands that threaten a debt-ceiling showdown. If Republicans want to have conversations about future defense cuts that are strategic, then I am open to that,” Khanna told the Guardian. “While I support the funding for Ukraine’s defense, we need to take ourselves off the path to a trillion-dollar Pentagon budget.”

Progressive advocates similarly rejected the notion that the US must choose between cutting the Pentagon’s budget and supporting Ukraine. Stephen Miles, president of the progressive group Win Without War, blamed the Pentagon’s ballooning budget on ineffective weapons systems and excessive contracts to private companies, which have accounted for as much as half of US defense spending in recent years.

“The spending on Ukraine is not what’s driving the Pentagon’s growth,” Miles said. “We’re talking about major weapon systems procurement; we’re talking about private service contracting. We’re talking about a lot of things that aren’t being driven by Ukraine.”

Duss, now a visiting scholar at the Carnegie Endowment for International Peace, said the war in Ukraine should not prevent any debate over defense spending. He noted that politicians like Sanders and Lee have demanded reductions in the Pentagon’s budget for years, long before the war in Ukraine began.

“There’s always going to be some crisis of the moment that prevents us from thinking about how to spend less on defense,” Duss said. “But this is a conversation that we absolutely have to have.”

As of now, the prospects for enacting Pentagon budget cuts appear bleak. Even some of the House Republicans who, like Gaetz, initially opposed McCarthy’s speakership bid have downplayed the possibility. Congressman Chip Roy of Texas, a key negotiator in the talks between McCarthy and his Republican detractors, claimed that “cuts to defense were NEVER DISCUSSED” during the speakership fight.

“In fact, there was broad agreement spending cuts should focus on NON-DEFENSE discretionary spending,” Roy’s office said on Twitter.

A funding bill that solely cut non-defense discretionary spending would almost certainly be rejected by Democrats, who still control the Senate and the White House. In addition to the procedural hurdles of Roy’s proposal, Miles mocked the idea of excluding defense spending from potential cuts as utterly unrealistic.

“You can’t look at the level of spending that the US government is doing and say we’re going to exempt more than half of discretionary spending,” Miles said. “When you have the Pentagon taking up as much money as it is now, there’s no way to look at cutting government spending without it.”

Even if Congress could somehow reach an agreement on the need to reduce the Pentagon’s budget, conservatives would inevitably clash with progressives over what programs to cut and how to reallocate that funding.

“The reason Matt Gaetz wants to cut defense spending is not the reason why I would,” Duss acknowledged.

Still, Duss argued that progressives and some lawmakers on the right have a “shared interest” in starting a reinvigorated conversation over defense spending. That communal goal could work to progressives’ advantage.

“If Republicans want to prize this open and look inside this budget … that’s a debate I think everyone should welcome,” Duss said. “And I think it’s quite telling who’s not welcoming it.”