WASHINGTON — A broadly supported bill to expand medical care eligibility for millions of veterans who may have been exposed to toxins from burning pits of trash on U.S. military bases has become ensnared in a partisan fight over spending, leaving its fate uncertain after a large group of Republicans pulled their support.
The legislation, which would be one of the largest expansions of veterans benefits in history, had been expected to easily pass the Senate last week after receiving an overwhelming bipartisan vote in the House. An earlier version passed the Senate in June on a lopsided vote, with 34 Republicans voting in favor.
But Republicans abruptly withdrew their backing, with all but eight opposed to moving forward on it last week. They did so after Senator Patrick J. Toomey, Republican of Pennsylvania, raised concerns that the measure — which would create a new entitlement program within the Department of Veterans Affairs to finance treatment for veterans exposed to toxins — could lead to vast spending increases.
The reversal also came after Democrats struck a surprise deal to push through a sweeping climate, energy and tax plan this month over unified Republican opposition — a central piece of their domestic agenda that Republicans have derided as a spending spree.
Senator Chuck Schumer, Democrat of New York and the majority leader, said on Sunday that he planned to schedule another vote on the veterans bill this week.
Republicans’ turnabout has stunned proponents in Congress and veterans groups who had seen the burn pits legislation, a top priority of President Biden, as a done deal.
In the days since, veterans have gathered at the Capitol on the steps leading to the Senate, holding signs, photographs of lost loved ones and flags protesting the legislative delay and standing vigil, even during rain over the weekend. The comedian Jon Stewart, a leading activist on the bill, said at a news conference last week that the veterans were not planning to leave until lawmakers took action.
Exposure from trash fires is believed to have led to a number of ailments and respiratory illnesses among veterans such as bronchial asthma, allergic rhinitis, sleep apnea, bronchitis and sinusitis, as well as different kinds of cancer. The issue has been especially poignant for Mr. Biden, who has speculated that toxic exposure contributed to the death of his son Beau Biden, who died in 2015 several years after serving in Iraq.
The measure would create a new, guaranteed funding stream — not subject to congressional appropriations — for treating veterans exposed to toxins. Republicans warned that could lead to vast, unchecked spending by the Department of Veterans Affairs.
“We want to make sure the PACT Act is not used as a vehicle to dramatically increase spending outside of the objective of the bill, which is to cover specific health care and benefits for veterans,” Mr. Toomey said last week.
He proposed imposing an annual cap and ending the entitlement after 10 years, meaning the funding to care for veterans exposed to toxins would not be guaranteed unless Congress voted to provide it.
Denis McDonough, secretary of the V.A., said on CNN’s “State of the Union” on Sunday that the proposal would lead to the “rationing of care for vets.”
Senator Jon Tester, Democrat of Montana and the chairman of the Veterans Affairs Committee, decried Republicans’ reversal, saying that by blocking the bill’s enactment, they essentially “took benefits away from the people who have been impacted by a war that we set off.”
Mr. Tester and some other Democrats said they plan to apply pressure on Republicans to get them to switch positions again and support the bill. Mr. Schumer has said he will allow Republicans a chance to offer their own proposal for funding the measure.
At issue is legislation that would affect an estimated 3.5 million veterans and rival the Agent Orange Act that increased access to care for Vietnam War veterans exposed to the toxic substance that was used as an herbicide and endangered generations of Vietnamese, Laotians and Cambodians.
The bill would make it easier for American service members stationed in a combat zone for the past 32 years to be eligible for V.A. medical care and allocate a projected $280 billion over the next decade to treat ailments tied to those exposures.
It also orders the department to recognize dozens of cancers and illnesses that could be linked to toxic exposure and include such exposures in patient questionnaires to reach patients who might be unaware that their condition could be linked to burn pits. Benefits would be phased in over time, meaning veterans discharged more recently would have to wait more than a decade to receive care.
As of July, more than a third of all veterans deployed to Southwest Asia since Sept. 11, 2001, have submitted a disability claim for compensation related to respiratory conditions, making them the most common ailments, according to the agency. Of those who filed a claim, only 64 percent were granted.
Advocacy groups that have been tracking the legislation said they had been heartened by reports that the measure could soon be back on track.
Sarah Verardo, CEO of The Independence Fund, a nonprofit organization dedicated to helping wounded veterans said the group has “been monitoring congressional movement over the weekend” and is “very optimistic in leadership tone shift.”