Wal-Mart Stores said it will stop selling sales information to third-party gatherers of retail sales data about the clothing, food, beverages and thousands of other products it sells in its stores, making it more difficult for competitors, suppliers and analysts to study the world's largest retailer and industry trends.

Wal-Mart cited competitive interests for its decision to stop sharing data gathered by electronic scanners in the checkout aisle. The data are used by other companies to gauge the performance of the products they sell through Wal-Mart.

"We can learn as much as we were learning from this information through other sources, without having to disclose our own sales," a company spokesman was quoted as saying in the New York Times.

Wal-Mart shares sales data with six market research firms, five of whom will be cut off in July. They include ACNielsen, a unit of VNU NV in the Netherlands, and Information Resources Inc in Chicago. A sixth firm, which collects data on sporting goods, will get information through the end of the year, when its contract expires.

Information Resources has told customers it will try to persuade Wal-Mart to reconsider. If it fails, it said it has developed new tools to project Wal-Mart sales.