WASHINGTON — Add another, more prosaic item to the list of things Congress has left until the last minute to resolve this year: the price of milk.

Distracted by dealing with the Bush tax cuts, lawmakers are running out of time to pass the latest version of the country’s sweeping farm bill and avoid what’s become known as the “dairy cliff.” If Congress misses the Jan. 1 deadline, the price of milk could rise significantly — some say by more than $3 a gallon — as the country’s farm policy reverts back to laws dating from 1949.

The Agriculture Department said prices would not jump immediately in 2013 and that the agency is exploring all options for heading off a mess. But hopes are diminishing that lawmakers will deal with the farm bill in time to avoid throwing the nation’s farm policy back more than six decades.

“The best outcome would be for Congress to do its job and pass a five-year bill,” Agriculture Secretary Tom Vilsack said last week. “The worst outcome is for us to continue to see Congress do nothing and for permanent law to come into effect.”

It’s not just milk that’s in limbo. The farm bill also includes disaster relief for farmers and foreign food aid that expired Oct. 1 because of inaction.

And if Congress does not pass the bill by March, when it’s time for farmers to start planting crops, the antiquated laws could begin to roil production for other products, from peanuts to corn, by applying quotas discarded years ago.