Wal-Mart Stores Inc. (WMT) Monday maintained its July sales forecast, and said the vital back-to-school shopping season was off to a good start.

On a recorded message updating sales through July 16, the world's biggest retailer said it still expects a 2 percent to 4 percent gain in July sales at its U.S. stores open at least a year.

Bentonville, Ark.-based Wal-Mart listed food, paper goods and pet supplies among the best-selling categories last week, and said price inflation was largely responsible for boosting its sales tally in paper goods.

Paper goods makers, including Kimberly-Clark Corp. (KMB) and Procter & Gamble Co. (PG), have announced price increases on tissues and other goods in recent months to make up for rising pulp and energy prices.

Analysts have been watching closely to see whether Wal-Mart would pass those increases along to customers or keep prices flat at its stores, which would put even more pressure on suppliers to cut costs elsewhere.