The two biggest U.S. warehouse retail chains are limiting how much rice customers can buy because of what Sam's Club, a division of Wal-Mart Stores Inc., called on Wednesday "recent supply and demand trends."

The two biggest U.S. warehouse retail chains are limiting how much rice customers can buy because of what Sam's Club, a division of Wal-Mart Stores Inc., called on Wednesday "recent supply and demand trends."

The broader chain of Wal-Mart stores has no plans to limit food purchases, however.

The move comes as U.S. rice futures hit a record high amid global food inflation, although one rice expert said the warehouse chains may be reacting less to any shortages than to stockpiling by restaurants and small stores.

Sam's Club followed Seattle-based Costco Wholesale Corp.'s, which put limits in at least some stores on bulk rice purchases.

Sam's Club said the limits affect 20-lb bags, not retail-sized portions. Costco could not immediately be reached for comment on its limits or whether they are the first ever.

Sam's Club said it will limit customers to four bags at a time of imported jasmine, basmati and long grain white rice.

The warehouse chain caters heavily to small businesses, including restaurants. Sam's Club spokeswoman Kristy Reed said she could not comment on whether the problem was caused by short supplies or by customers stocking up in anticipation of higher prices.

USA Rice Federation spokesman David Coia said there is no rice shortage in the United States.

"It's possible that small restaurants and bodega-type neighborhood stores may be purchasing rice in larger quantities than they do typically to avoid higher prices," Coia said about the warehouse chain restrictions.