NEW YORK (CNN/Money) - Wal-Mart Stores Inc. and Federated Department Stores Inc. said Monday they expect September sales at stores open at least a year to be near the low end of forecasts.

Retailers are closely monitoring consumer behavior and spending these days as uncertain economic news, concern over a possible invasion of Iraq and corporate scandals appear to be making Americans more cautious in their spending.

Wal-Mart, the world's biggest retailer, did not provide details of its September forecast, but the chain had expected a 4-6 percent increase. Shares of Wal-Mart, (WMT: down $2.45 to $52.25, Research, Estimates) one of 30 components that make up the Dow Jones industrial average, fell more than 4 percent Monday, helping send the Dow lower.

But it doesn't necessarily follow Wal-Mart is headed for a fall. An increasingly cautious consumer has been trained over the last decade to wait for bargains, particularly when times get tough.

"Purchasing patterns have been changing for a long time. It used to be you bought for Christmas when you bought for back-to-school. Today, there's no reason to buy ahead of your need when you can buy it when you need it at a better price," Todd Slater, a retail analyst at Lazard Freres & Co. LLC, said.

Even though sales may be slowing, that doesn't necessarily mean consumers are going to stop shopping at discount chains, reversing overnight a trend that started a decade ago.

Bentonville, Ark.-based Wal-Mart said in a pre-recorded announcement Monday that store traffic increased after the Sept. 11 anniversary and that best-selling departments included home furnishings, electronics, intimate apparel, health and beauty aids, pharmacy and food.

In August, Wal-Mart, whose sales are considered a retail barometer by many investors, also had forecast a 4-6 percent same-store sales increase, but ended up reporting a 3.8 percent gain.

Overseas, the company's United Kingdom and Korean units turned in the best performance of the International division last week.

Meanwhile, Federated Department Stores Inc., operator of Macy's, Bloomingdale's and other chains, said it also expects September sales to fall at the low end of its expectations of a 3-5 percent increase.

Cincinnati-based Federated said that even though sales are running well ahead of the same period last year, they came in slightly below expectations last week.

"This is a difficult time to be forecasting sales," the company said in a pre-recorded announcement.

Federated's (FD: down $1.57 to $33.22, Research, Estimates) shares were down 4.7 percent in trading Monday.

J.C. Penney (JCP: down $0.14 to $18.12, Research, Estimates) said Monday that sales at its department stores are on track with expectations for a flat to slightly higher increase in September than a year ago and that sales at its Eckerd drugstore division also are on track for forecasts of a 6-8 percent same-store sales increase in September.

Shares of Plano, Texas-based J.C. Penney were down slightly Monday.