Wal-Mart Stores Inc. predicted a rare decline in monthly sales on Saturday, even as U.S. bargain-hunters jammed stores in search of gifts at the start of the crucial holiday shopping season.

Wal-Mart, the world’s biggest retailer, sounded a cautious note for retailers as they began a second day of Thanksgiving weekend sales with deep discounts and early bird specials on items ranging from cashmere sweaters to big-screen plasma televisions.

Wal-Mart estimated that November sales fell 0.1 percent at its U.S. stores open at least a year — a closely watched retail measure known as same-store sales.

The retailer will provide a final monthly sales report on Thursday, when most other major chain stores report their November figures. This would mark Wal-Mart’s first monthly same-store sales decline since April 1996.