WASHINGTON — The top leaders in both parties on the House and Senate Agriculture committees have agreed to a one-year extension of the 2008 farm bill that expired in October, a move that could head off a possible doubling of milk prices next month.

Senate Agriculture Committee Chairman Debbie Stabenow, D-Mich., indicated the House could vote on the bill soon, though House leaders have not yet agreed to put the bill on the floor. In addition to the one-year extension that has the backing of the committees, the House GOP is also considering two other extension bills: a one-month extension and an even smaller bill that would merely extend dairy policy that expires Jan. 1.

Expiration of those dairy programs could mean higher prices at the grocery store within a few weeks. Agriculture Secretary Tom Vilsack said Americans face the prospect of paying $7 for a gallon of milk if the current dairy program lapsed and the government returned to a 1948 formula for calculating milk price supports.