WASHINGTON — The fight over renewing the nation’s farm bill has centered on cuts to the $80 billion-a-year food stamp program. But there could be unintended consequences if no agreement is reached: higher milk prices.

Members of the House and Senate are scheduled to begin long-awaited negotiations on the five-year, roughly $500 billion bill this week. If they don’t finish it, dairy supports could expire at the end of the year and send the price of a gallon of milk skyward.

There could be political ramifications, too. The House and Senate are far apart on the sensitive issue of how much money to cut from food stamps, and lawmakers are hoping to resolve that debate before election-year politics set in.

Minnesota Sen. Amy Klobuchar, a Democrat who is one of the negotiators on the bill, says the legislation could also be a rare opportunity for the two chambers to show they can get along. “In the middle of the chaos of the last month comes opportunity,” Klobuchar says of the farm legislation.

The farm bill, which sets policy for farm subsidies, the food stamps and other rural development projects, has moved slowly through Congress in the last two years as lawmakers have focused on higher-profile priorities, like budget negotiations, health care and immigration legislation.

But farm-state lawmakers are appealing to their colleagues to hearken back to more bipartisan times and do something Congress hasn’t done very much lately — pass a major piece of legislation.

Even President Barack Obama, who has been largely silent on the farm bill as it has wound through Congress, said as the government reopened earlier this month that the farm bill “would make a huge difference in our economy right now.”

The main challenge in getting the bill done will be the differences on food stamps, officially called the Supplemental Nutrition Assistance Program, or SNAP. The House has passed legislation to cut around $4 billion annually, or around 5 percent, including changes in eligibility and work requirements. The Senate has proposed a cut of around a tenth of that amount.

“I think there are very different world views clashing on food stamps and those are always more difficult to resolve,” says Roger Johnson, president of the National Farmers Union.

Johnson says coming together on the farm issues will be easier because the mostly farm-state lawmakers negotiating the bill have common goals.