NEW YORK (CNN/Money) - Two of the nation's biggest retailers Monday reported sluggish sales in the first half of December, as the holiday season struggled to move into high gear with little more than a week left before Christmas.

Wal-Mart Stores Inc. said that December sales at stores open at least a year, a key gauge known as same-store sales, were tracking at the low end of forecasts, and Federated Department Stores said that same-store sales for the combined November/December period were also tracking at the low end of expectations.

Wal-Mart said the slower sales in part reflected consumers' tendency to hold off purchases until close to the need, something industry analysts agree is happening as shoppers worry about the economy and a potential war with Iraq.

"I think consumers are more cautious, and I think the retailers have kept inventories well under control," said Delos Smith, an economist with the Conference Board, a private New York-based business research group.

Ellen Tolley, a spokeswoman for the National Retail Federation, the industry's largest trade group, said activity should pick up in the next few weeks, especially since indications are that many people have not yet completed the bulk of their holiday shopping.

"There were a lot of people out in the stores this past weekend, and from the looks of things, it seems like a lot of people have a lot of shopping left to do. It's going to be a busy next two weeks," Tolley said.

Meanwhile, Wal-Mart said in a pre-recorded message Monday it still expects to achieve December sales increases of 3-to-5 percent over last year, but that sales through the second week of December are tracking at the low end of that forecast.

The world's largest retailer said sales of seasonal holiday items picked up last week after being slow the previous week. Other strong categories were fabrics and crafts, bedding, intimate apparel, hardware and pharmacy sales.

Shares of Bentonville, Ark.-based Wal-Mart (WMT: Research, Estimates) slipped 84 cents to $50.54 Friday.

Federated Department Stores Inc. said it continues to expect combined sales for November and December at the low end of its forecasts for flat-to-down 2.5 percent compared with a year ago.

Federated, the parent of Macy's and Bloomingdale's, said it remains difficult to gauge total holiday season performance. But many retailers are bracing for a more sluggish season than a year ago in anticipation of tighter spending by consumers amid a lackluster economy and worries about a war with Iraq.

Shares of Cincinnati-based Federated (FD: Research, Estimates) slipped 85 cents to $28.73 Friday.

Separately, J.C. Penney Inc. (JCP: Research, Estimates) said it expects a low-single-digit increase for December same-store sales and that sales through last week were on track to achieve that target. The Plano, Texas-based chain also said it expects a 6 percent increase in same-store sales at its Eckerd drugstore chain in December.

J.C. Penney shares lost 46 cents to $23.60 Friday.