Wal-Mart Stores Inc. (WMT.N: Quote, Profile , Research) estimated on Saturday that December sales rose 1.6 percent at its U.S. stores open at least a year, beating its forecast, in the heaviest shopping period of the year.

The world's biggest retailer had expected same-store sales to be flat to up 1 percent. Wal-Mart and most other major U.S. retailers will release final December sales data on Thursday.

Wall Street is watching holiday sales particularly closely this year for clues on how consumer spending is holding up in the face of a slowing housing market.

Analysts have been bracing for disappointing holiday season sales, particular among clothing chains, after unusually mild December weather in many parts of the country crimped demand for winter apparel.

For November, Wal-Mart posted its first same-store sales decline in more than a decade, despite aggressive discounts on products ranging from food to flat-panel televisions.

The poor November showing cast doubt on Wal-Mart's fourth-quarter earnings prospects. The retailer is expected to update its profit forecast on Thursday.

Wal-Mart's closest competitor, Target Corp. (TGT.N: Quote, Profile , Research), said on December 18 that its December same-store sales were on track to meet its forecast for 3.5 percent to 5.5 percent growth.