NEW YORK - Kroger Co , the largest U.S. grocery chain, reported a much lower-than-expected quarterly profit and cut its full-year forecast as it feels pressure from falling food prices and stepped up competition, pushing its shares down nearly 10 percent in premarket trade.

The Cincinnati-based company, which operates stores under its own name as well as Ralphs, King Soopers, Fry's and Food 4 Less, reported a net loss of $874.9 million, or $1.35 per share, for the third quarter ended November 7, while it had a profit of $237.7 million, or 36 cents per share, a year earlier.

Excluding an impairment charge stemming from a writedown at its Ralphs division, Kroger earned 27 cents per share. Analysts, on average, expected a profit of 37 cents per share, according to Thomson Reuters I/B/E/S.

Total sales at Kroger, which also runs the Littman and Barclay jewelry chains, edged up 0.3 percent to $17.67 billion, weighed down by the lower price of the gasoline it sells.

Kroger now expects to earn $1.60 to $1.70 per share this year, down from its prior forecast of $1.90 to $2.00 per share.

The economic downturn has intensified competition among grocery sellers and chains ranging from Wal-Mart Stores Inc to Kroger, Safeway Inc , Supervalu Inc and even the more upscale Whole Foods Market Inc are fighting for every customer.

(Reporting by Phil Wahba and Lisa Baertlein, editing by Dave Zimmerman)