Supermarket operator Kroger Co posted quarterly profit below Wall Street estimates and trimmed its full-year forecast, sending its shares down 6.3 percent.

The Cincinnati-based company, which operates stores under its own name as well as Ralphs and Food 4 Less, has seen its sales pressured amid high unemployment.

Grocery stores, including those owned by Kroger, have also been lowering prices as they compete with Wal-Mart Stores Inc, the largest seller of groceries in the United States. Shares of rival Safeway Inc fell 3.5 percent after the Kroger report on Tuesday, while Supervalu Inc slipped 2.8 percent.

Kroger said net income fell to $254.4 million, or 39 cents per share, in the second quarter, ended Aug. 15, from $276.5 million, or 42 cents per share, a year earlier.

For the year, the company now expects earnings of $1.90 to $2.00 a share, down from its previous forecast of $2.00 to $2.05. Analysts' average forecast is $2.04, according to Reuters Estimates.

Total sales at Kroger, which also runs the Littman and Barclay jewelry chains, fell 2.2 percent to $18.1 billion, weighed down by the lower price of the gasoline it sells.

Excluding fuel, sales rose 3.5 percent.

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