The company also lowered its 2009 earnings forecast.

The owner of the Albertsons, Jewel-Osco, Shaw's and Save-A-Lot chains posted a loss of $2.94 billion, or $13.95 a share, for the fiscal third quarter ended November 29, compared with a profit of $141 million, or 66 cents a share, a year earlier.

The loss included noncash impairment charges of $3.3 billion as the company wrote down the value of some assets.

Excluding the charges, earnings were 62 cents a share, compared with analysts' average estimate of 60 cents, according to Reuters Estimates.

Net sales edged down to $10.17 billion from $10.21 billion a year earlier. Retail food net sales were flat at $7.9 billion.

Closely watched identical-store sales fell 0.5 percent. Supervalu's identical-store sales include results from outlets operating for four full quarters, including store expansions, and exclude fuel sales.

Gross profit margin rose to 22.4 percent from 22.2 percent.

Supervalu, which has about 2,500 stores, has rolled out new products ranging from its Wild Harvest organic brand to a newer line of premium prepared meals. It is also testing a small-store format with ready-to-go entrees as well as basics like milk and produce.

The company said it now expects earnings of $2.80 to $2.90 a share for fiscal 2009 before one-time items, down from a previous forecast of $2.90 to $3.00.

Shares of the company stood at $15.09 in premarket trade, unchanged from Tuesday's close.

(Reporting by Brad Dorfman and Lisa Baertlein; editing by John Wallace)