Wal-Mart Stores Inc. , the world's largest retailer, said Thursday its sales at stores open at least a year rose 8 percent in December, topping company forecasts.

But even though December sales were better than expected, Wal-Mart said on a recorded conference call that it is sticking with its fiscal fourth-quarter earnings forecast of 48 cents a share because of continued pressure on gross margins.

The discount giant said it is seeing more customers in its stores, but they are buying lower-priced items.

Analysts polled by Thomson Financial/First Call on average expected Wal-Mart to report a profit of 48 cents.

Wal-Mart had forecast its sales growth in December would be at the upper end of a range of 4 percent to 6 percent. Wall Street analysts' estimates ranged from 5 percent to 8 percent.

The retailer said net sales in the five weeks ended Jan. 4 rose 16.2 percent to $28.84 billion from $24.82 billion a year earlier.

At outlets open at least year, sales at Wal-Mart discount stores rose 8.2 percent last month, while sales at its warehouse unit Sam's Club were up 7.1 percent.

For January, Wal-Mart said it expects same-store sales to increase 4 percent to 6 percent.