Congress is feuding over a new farm bill, making lawmakers likely to punt the matter for another year and leave American farmers and families on food assistance without an update to the legislation that controls how much federal support they receive.

Republicans and Democrats agree it is time for an updated bill. The last one was written in 2018 and expired two years ago, meaning American farmers are trying to run their businesses based on 6-year-old policy.

But the two parties cannot get past a core dispute over how to pay for it. Republicans want to cut nutrition assistance for the poor to pay for bolstered financial support for farmers, while Democrats refuse to reduce food support for low-income people. The disagreement is likely to only deepen next year, with President-elect Donald J. Trump in the White House and Republicans in total control of Congress.

“A lot has changed in our world since 2018 and the last farm bill,” said Robert Guenther, a former House Agriculture Committee aide and an agriculture policy expert who represents tomato growers in Florida. “We’re kind of stuck in limbo with old policy that needs to be modernized and reinvigorated.”

Underneath the policy fight also lies a political subplot. Senator Debbie Stabenow of Michigan, the Democratic chairwoman of the Agriculture Committee who has been her party’s leading voice on the issue for more than a decade, will retire in January.