Last month's expiration of ethanol subsidies from the U.S. federal government may already be driving up gas prices.

Average gas prices as of Friday were $3.39 a gallon, up three cents from a week ago and up from $3.26 a month ago, according to AAA. Fuel prices for the three weeks ended January 6 rose 12 cents to $3.36 a gallon, marking the first three-week increase since late October, Bloomberg News reported earlier this week, citing Lundberg Survey Inc. Bloomberg said prices rose almost 28 cents from a year earlier.

The culprit may be the end of thirty years of subsidies for corn-based ethanol. By failing to vote in an extension, Congress allowed the $0.45 per gallon production subsidy to expire with the start of 2012. With an annual payout of $6 billion, the subsidy was a popular target for politicians looking to show their dedication to reducing the deficit, but its expiration may have triggered a 4.5-cent increase in cost for gasoline suppliers.

Such rising fuel prices may spell further bad news for consumers already battered by record refueling costs last year. Average gas prices jumped about 27 percent last year to $3.53 a gallon, and fuel prices surpassed the $4 threshold last May. As a result, vehicle-refueling costs totaled more than $4,100 for the typical U.S. household in 2011 and likely accounted for the largest percentage of a average U.S. family's annual income since 1981, the Associated Press reported late last month.