The bill would increase food-stamp spending by 2.5 percent, or $620 million annually. A proposal by Sen. Richard Lugar, R-Ind., to add another $1 billion was defeated Wednesday 70-30.

Lugar's plan would have scrapped existing farm subsidy programs, which primarily benefit large grain and cotton farms, offered direct payments to all producers.

"Now is not the time to pull the rug out from under our farmers for a program that has not been tested," said Senate Agriculture Committee Chairman Tom Harkin, D-Iowa.

"Even though we might want to do more for nutrition, I think we've met our responsibilities in this bill," Harkin said.

The bill would restore food-stamp benefits to some legal immigrants and also streamline the application process and slightly boost monthly benefits.

A proposal by Sen. Judd Gregg, R-N.H., to reduce benefits to sugar growers was defeated 71-29. The savings would have been put into the food-stamp program, he said.

The farm bill would reauthorize programs set to expire next fall. Agriculture groups are pushing Congress to quickly finish work on the legislation for fear that there will be less money available for their subsidies if Congress waits until next year.

Democratic leaders hope to get Senate approval for the bill by the end of the week.

But Republicans say the bill, which would sharply boost crop subsidies, would encourage excess production and drive down commodity prices. The House passed its version of the farm bill in October.

Sen. Thad Cochran, R-Miss., said it was "pie in the sky" to think that lawmakers could iron out differences between the House and Senate bills by Christmas.

Sen. Pat Roberts, R-Kansas faulted farmers' representatives for not reviewing policy. "Too many farm organizations have simply come in and viewed the farm bill as an ATM machine," he said.

The Democratic bill "stomps down" commodity prices, Lugar said. "They have no chance to come up."

The Bush administration endorsed Lugar's farm plan this fall but it never attracted support from agriculture groups. Lugar said it would be better for growers in the long run to reduce their dependence on the government.

Farmers could have used the vouchers to buy revenue insurance or to take other measures to control their financial risk.

Senators agreed to keep a provision in the Democratic bill that would allow landowners in the West to lease their water rights to the government under a farm conservation program. Individual states could decide not to participate in the program.

On Tuesday, the Senate rejected 51-47 a Republican move to kill $2 billion in new dairy subsidies that are part of the bill.

The Bush administration says the Democratic bill could break both spending caps in this year's congressional budget agreement and a limit on U.S. farm subsidies under the World Trade Organization.

Breaking the WTO cap would undermine the administration's efforts to get other countries to reduce their subsidies and open new markets for U.S. commodities, the White House said in a policy statement.

The Democratic bill is designed to increase farm spending by $73.5 billion over 10 years, the limit sent in the budget deal. However, Democrats have earmarked about $45 billion of that spending in the first five years in order to expand conservation programs.