Majority Leader Harry Reid says the Senate will not extend current farm law if Congress can't agree on a new farm bill before adjourning next week.
House leaders have reserved space on their agenda this week for extending the current law until the end of January. Lawmakers fear that milk prices might rise sharply if dairy subsidies expire Jan. 1.
The House and Senate have passed separate versions, but with widespread differences over crop subsidies and how much to cut food stamps.
(Read more: 'Dairy cliff': Why milk may soar to $8 a gallon)
Speaker John Boehner, R-Ohio, said last week that the House should extend the current law while negotiators seek a compromise.
The response Tuesday from Reid, D-Nev.: "Let them vote on it. We're not going to do it."
Some senators fear an extension relieves pressure to get a deal.
—By The Associated Press.