Groceries accounted for 51% of Wal-Mart Stores Inc.’s U.S. sales last year, the first time the category garnered more than half the retailer’s revenue.

With a 51% share of total revenue, Wal-Mart’s U.S. grocery sales generated about $131.7 billion in the company’s fiscal 2010, based on a March 30 filing with the U.S. Securities and Exchange Commission.

Groceries accounted for 49% of U.S. sales in 2009, Wal-Mart said in the filing.

The figures illustrate Bentonville, Ark.-based Wal-Mart’s expanding reliance on groceries and its growing dominance in food retailing. Groceries are by far Wal-Mart’s biggest merchandise category, with the next-biggest, entertainment, accounting for 13% of 2010 sales.

Wal-Mart’s share of the $816 billion U.S. retail food business is expected to rise to 21.6% in 2010 from 20.5% in 2009, Citigroup Inc. analyst Deborah Weinswig said in a report last month.

In a March 10 investor presentation, Wal-Mart chief operating officer Bill Simon said the company will accelerate “rollbacks,” or permanent price reductions. Analysts say that with more aggressive rollbacks, Wal-Mart is going after Kroger Co. and other major supermarket chains that drew customers away in recent years.

“We’re always about price,” Simon said March 10. “We have to deliver price, and we do.”

Wal-Mart’s U.S. stores, excluding Sam’s Club, had sales of $258.2 billion in the company’s fiscal 2010, which ended Jan. 31. The 2010 sales were up 1.1% from $255.4 billion in 2009.

(Note on correction: An earlier version of this story had an incorrect dollar amount regarding Wal-Mart's fiscal 2010 sales figures).

Wal-Mart's grocery sales increase