Lawmakers working on an election-year overhaul of farm and nutrition programs canceled a public meeting Friday as the negotiations turned more serious, aides said.

"They're trying to make some progress towards some sort of deal," said Seth Boffeli, a spokesman for the chief Senate negotiator, Tom Harkin, D-Iowa. "It might take the weekend. They might get something formulated closer to the middle of next week."

A House-Senate conference committee held long public sessions Tuesday, Wednesday and Thursday to air differences on a wide range of issues, including new rules for crop subsidies and meatpackers, as well as President Bush's proposal to restore food stamps to immigrants.

Leaders of the conference committee, including Harkin and Rep. Larry Combest, R-Texas, met privately Friday morning and there were additional sessions expected through the weekend, aides said.

Farm groups have been pushing lawmakers to finish work on the legislation in time for it to apply to this growing season.

Meanwhile, two senators say Senate-passed limits on individual farm subsidies could save taxpayers a lot more money than first thought, based on new government data released by an environmental group.

Growers have collected $1.5 billion over the past six months under a program that allows big farms to avoid the normal limits on crop subsidies. That program, which primarily benefits cotton and rice producers, has soared in popularity since it was approved by the Clinton administration in 2000.

The Senate voted in February to abolish the program and tighten limits for other subsidies. At the time, congressional budget analysts estimated those measures would cut federal spending $1.4 billion over 10 years, or about $140 million annually.

Sens. Charles Grassley, R-Iowa, and Byron Dorgan, D-N.D., asked the analysts to quickly review their estimate.

"Congress needs to decide how much taxpayers should be on the line for endless subsidies to production," said Anne Keys of the Environmental Working Group, which released the subsidy data.

The Associated Press reported last year that a real estate developer had used the program to collect more than $1 million in subsidies on a series of farms he controlled.

The Senate-passed measure is one of the most contentious issues facing the conference committee. House negotiators are dominated by lawmakers from southern states who oppose any significant new limits on subsidies.

The government guarantees farmers a minimum return for their grain, cotton and soybean crops by providing subsidies when market prices fall below certain levels.