NEW YORK (CNN/Money) - Federated Department Stores said Monday it expects a key measure of its December sales was below year-ago levels, although competitor J.C. Penney beat its own expectations with strong department store sales.

Federated, owner of such chains as Macy's and Bloomingdale's, said in a recorded announcement that it expects sales at stores open at least a year, a closely watched measure known as same-store sales, to be off about 2.5 percent in December, plus or minus a couple of tenths of a percentage point. The December sales period runs through Jan. 4.

The decline is an improvement from the 7.4 percent drop in same-store sales in November. Overall, it expects same-store sales for the two-month period will be off 4.5 percent.

Plan, Texas-based J.C. Penney said its five-week December sales period will show a 4.5 percent gain in same-store sales for its department store unit, which it said was above plan due to strong sales in the final week of the period.

But Penney said its Eckerd drugstore unit won't meet its 6 percent growth target for same-store sales during the period. Eckerd now accounts for about 48 percent of the company's overall revenue.

Wal-Mart Stores Inc., the world's largest retailer, also released a weekly update, repeating its guidance of last Thursday that it expects same-store sales to be up 2 to 3 percent, and that same-store sales will be up about 3 percent at its core Wal-Mart unit, and its Sam's Club wholesale division will see same-store sales fall from a year ago. That guidance was slightly below the 3 to 5 percent gain it expected heading into the holiday period.

"It appears that even with us slightly missing our plan for the period, our holiday inventories are at manageable levels," Wal-Mart's recorded announcement said.

Shares of Wal-Mart (WMT: up $0.62 to $49.78, Research, Estimates), a component of the Dow Jones industrial average, were higher Monday morning while Federated (FD: down $0.02 to $27.50, Research, Estimates) and J.C. Penney (JCP: down $0.03 to $22.04, Research, Estimates) lost ground.