Wal-Mart Stores Inc. (WMT) on Thursday said fourth-quarter profit would likely reach only the low end of its forecast after a disappointing December.

The world's biggest retailer, which confirmed that December sales rose just 2.2 percent at its U.S. stores open at least a year, said it expects profit near the low end of its forecast of 82 cents to 86 cents per share.

Analysts, on average, expected 83 cents per share, according to Reuters Estimates.

"Wal-Mart dropped a bomb on the market with earnings guidance at the low end of its 82-86 cents range, as they clearly saw some margin pressure and most likely increased advertising and promotional expenses," said Ken Perkins, president of research firm Retail Metrics.

Wal-Mart got off to a fast start to the holiday season with aggressive advertising and discounts that helped drive strong November sales. But demand dropped early in December as shoppers waited until the last minute for deeper discounts.

As a result, Wal-Mart said the Friday before Christmas was the busiest shopping day of the year.

Demand for gift cards was particularly strong, which bodes well for January, and Wal-Mart forecast 3 percent to 5 percent same-store sales growth for that month. Retailers record revenue from gift cards when they are redeemed, not when they are sold, so that tends to deflate December sales.

Total sales for the five-week period ended December 30 rose 6.3 percent to $40.8 billion.

Shares of Wal-Mart dropped 19 cents, or 0.4 percent, to $46.13 on the New York Stock Exchange.