LOS ANGELES (Reuters) - Supermarket chain Supervalu Inc (SVU.N: Quote, Profile, Research) on Tuesday posted higher quarterly earnings on fewer charges, but weak sales prompted it to cut its full-year profit forecast and shares fell 6 percent.

The third-largest U.S. grocery store operator is grappling with record fuel prices at the same time that cash-crunched consumers have been cutting grocery bills by trading down to lower-cost store brands and generic medicine.

"This environment certainly is more volatile than we've had over a number of years," Supervalu Chief Executive Jeff Noddle said in a conference call.

"The ongoing weakness in the economy combined with higher food and energy inflation has created conditions that make us take a more cautious view for the balance of the fiscal year," he said.

Supervalu, whose chains include Albertsons, Jewel-Osco, Shaw's and Save-A-Lot, said profit was $162 million, or 76 cents a share, in the first quarter ended June 14 compared with $148 million, or 69 cents a share, a year earlier.

Analysts on average forecast 75 cents a share, according to Reuters Estimates.

Acquisition-related costs were 3 cents a share in the quarter compared with 8 cents a share a year earlier.

Sales were flat at $13.3 billion as a 4.6 percent increase in supply chain services sales helped offset a 0.7 percent decline in retail food sales, the company said. The company noted that it faced more store openings by competitors such as Wal-Mart Stores Inc (WMT.N: Quote, Profile, Research) in the quarter.

Closely watched identical-store sales were down 0.9 percent for the quarter. Supervalu's identical-store sales figure includes results from outlets operating for four full quarters, including store expansions, and excludes fuel sales.