The years-long fight over federal funding for food stamps is set for another showdown Thursday when House Republicans plan to vote on a proposal to dramatically curtail aid to needy Americans. Every Democrat is expected to vote against the proposal.

The GOP measure would slash about $39 billion over the next decade for food stamps, formally known as the Supplemental Nutrition Assistance Program, which is providing an average of $133 in monthly aid to more than 47 million Americans, according to a recent government report. The proposal differs sharply from a Senate plan passed this summer that would cut roughly $4.5 billion in SNAP money mostly by reducing administrative expenses.

Thursday’s vote will be a key test for House Majority Leader Eric Cantor (R-Va.), who abandoned four decades of congressional tradition this summer by splitting apart the farm bill to consider the nutrition funding separately. In July, the House narrowly approved a package that includes about $195 billion in crop subsidies over the next 10 years; that legislation proposes a wholesale overhaul for many agricultural and conservation programs and an end to direct payments to farmers.

The agriculture part of the plan mirrors provisions in a Senate farm bill passed in June.

But the nutrition proposals that the House is expected to vote on Thursday, reducing SNAP funding, are more controversial. They have the backing of dozens of conservative lawmakers who want deeper cuts in food aid and believe reductions cannot be made as part of a larger farm bill.

“People said it couldn’t be done, but we’re going to get it done here in the House,” said Rep. Marlin A. Stutzman (R-Ind.), part of a group of conservatives who worked with GOP leaders to craft the bill.

The bill would cut SNAP funding by stiffening the eligibility requirements for “able-bodied” people with no children. The Congressional Budget Office estimated this week that about 3.5 million adults would no longer be eligible for the program if the proposed changes are enacted.

The plan also would no longer allow states to waive those federal requirements for some ­able-bodied adults if the state has a high unemployment rate. But more than 40 states — including several led by Republican governors — want to extend their waivers in order to buoy low-income residents with federal aid during the economic recovery.

Aides representing lawmakers in both parties expect a narrow vote, though GOP aides insisted that they will earn the support of most House Republicans. Democrats suggested, however, that as many as 20 House Republicans from the Northeast and rural states with large low-income populations, who have previously rejected similarly dramatic cuts in food-stamp money, might vote against the bill.

“This is a new low,” House Minority Leader Nancy Pelosi (D-
Calif.) said this week as she announced that all 200 House Democrats plan to vote against the GOP plan.

If the bill with reduced SNAP funding passes, Republican leaders are expected to quickly launch negotiations with Senate Democrats over a final version of the farm bill, which would once again merge food aid with other agricultural policy. But Senate Agriculture Committee Chairman Debbie Stabenow (D-Mich.) rejected the GOP strategy Wednesday: “What the House Republicans are saying is this: Get a good-paying job or your family will just have to go hungry.”

Failure to pass a new farm bill by Sept. 30 risks rolling back federal farm policy to a 1940s-era law that would regulate the farming industry beginning in January.