When Joe Biden released his annual budget proposal last week, one number in particular jumped out to progressives: $813bn. That is how much Biden is calling to spend on national defense in the US in the coming fiscal year. If approved, that number would represent the largest defense budget that America has ever seen.

US presidents’ budget proposals are generally considered to be reflections of their policy priorities rather than realistic estimates of final spending allocations. If Biden’s call for a 4% increase in defense spending was meant to signal his policy priorities, progressives wasted no time in telling the president that his priorities are backwards.

Progressive lawmakers have fiercely criticized the proposed defense budget, arguing that the US already spends far too much on its military and needs to invest more in domestic programs. But the war in Ukraine has complicated progressives’ arguments and given Republicans an opening to demand even more money for the military.

Just hours after the White House announced its budget proposal on Monday, leaders of the Congressional Progressive Caucus released a statement attacking Biden’s plan to increase defense spending and opening up a familiar split in the party.

“It is simply unacceptable that after the conclusion of our longest war and during a period of Democratic control of both chambers of Congress, the president is proposing record high military spending,” said the CPC chair, Pramila Jayapal, and former chairs Mark Pocan and Barbara Lee.

“Appropriators and advocates are constantly called to answer for how we will afford spending on lowering costs and expanding access to healthcare, housing, childcare services, on fighting the Covid-19 pandemic, and on combating climate change – but such concerns evaporate when it comes to the Pentagon’s endlessly growing, unaudited budget.”

Bernie Sanders, who chairs the Senate budget committee, echoed the CPC’s concerns, saying on Monday, “At a time when we are already spending more on the military than the next 11 countries combined, no we do not need a massive increase in the defense budget.”

So far, the White House has stood by its request, insisting the increased funding will allow the US to better defend its international interests and assist Ukraine’s battle against Russia’s military assault.

“As I have said many times, we need resources matched to strategy, strategy matched to policy and policy matched to the will of the American people,” the defense secretary, Lloyd Austin, said. “This budget gives us the resources we need to deliver on that promise.”

And even as progressives urge Biden to curb funding for the military, the president is simultaneously facing criticism from the right for not proposing an even higher defense spending hike in response to the war in Ukraine.

“The world is a dangerous place and growing more dangerous by the day,” the Senate minority leader, Mitch McConnell, said on Monday. “Amid all this, the White House has proposed no meaningful increase in resources for protecting innocent Americans, promoting our interests, supporting our partners, assisting Ukraine, or replenishing our stockpiles.”

Progressives have pushed for years to lower US defense spending, but the devastation in Ukraine has added a new challenge to their efforts. Polling indicates that a majority of Americans believe Biden has not been tough enough in his response to Russia’s aggression, which has added fuel to Republicans’ demands for more military funding.

But progressives are not abandoning their campaign, instead arguing that the Russian invasion of Ukraine demonstrates how US military dollars would be better spent elsewhere.

“I think it’s a political challenge, but it’s not an actual budgetary challenge. This increase in money is not about Ukraine. This is about spending more on the US military-industrial complex,” said Robert Weissman, president of the progressive group Public Citizen. “The United States already spends more than 10 times what Russia does on its military. And that expenditure, obviously, didn’t deter Russia from invading Ukraine.”

Even as Republicans point to the war in Ukraine to advocate for more defense spending, it is worth remembering that most of Biden’s budget proposal was crafted before the Russian invasion.

Dr Travis Sharp, budget studies director at the Center for Strategic and Budgetary Assessments, said the requested funding increase is more a reflection of how record-high US inflation has affected government agencies’ finances rather than the impact of the crisis in Ukraine.

“Providing a higher level of defense spending does help to correct for some of the decreasing buying power as a result of inflation,” Sharp said. “If you didn’t provide a higher level of defense spending, then you would be trying to support the same-sized military with less money, so that would force you to make some hard trade-offs.”

However, progressives reject inflation-based arguments for increasing the Pentagon’s budget, saying the Pentagon has consistently failed to account for how it spends its funds and should not be trusted with even more money.

“An agency that can’t pass an audit needs to do a little bit more homework before we can be honest about what the impacts of inflation are,” said Stephen Miles, president of the progressive group Win Without War. He added, “Republicans don’t seem particularly concerned about the impacts of inflation on any other part of the budget, besides the military.”

As the number of US coronavirus deaths nears 1 million and the world faces the grim realities of climate change, it was “unconscionable” to demand more funding for the military, Miles said.

“The threats we face in the 21st century are primarily not going to be solved by spending more money at the Pentagon,” he told the Guardian.

For Sharp, the Pentagon’s significant budget is a reflection of America’s military commitments around the world and its strategy to maintain strong alliances with key foreign partners. He suggested that, in order for progressives to be successful in their push to lower defense spending, they need to make a pitch for a new kind of American foreign policy.

“If you really want to reduce the size of US defense spending, then you need to go after the strategy,” Sharp said. “If you pare back the strategy, reduce the operational tempo, then the dollars will decline proportionately.”