An RFID tag carries tiny silicon microchips attached to antennas.

Wal-Mart Inc. set off a scramble in the retail supply chain last year when it summoned its top suppliers to its Arkansas headquarters to lay down the law: Cases and pallets shipped to Wal-Mart by Jan. 1, 2005, would carry tags based on technology known as radio frequency identification, or RFID, to better track products.

Today, a week before the deadline, the so-called "Wal-Mart mandate" to replace bar codes with the bookmark-sized RFID tags is moving forward in fits and starts. But the Jan. 1 start-up date is shaping up as something less than the Big Bang many had expected for a technology that had its roots at MIT's Auto-ID Center and has been championed by a retailing goliath known for its ruthless efficiency.

Faced with technology hurdles, foot-dragging by suppliers, and costly up-front investments with little short-term return, Wal-Mart has confined its initial launch to pilot programs at a few distribution centers in Texas and seven stores in the Dallas-Fort Worth area. The retailer's 137 lead-off suppliers will be tagging cases and pallets for, on average, only 65 percent of products, with laggards tagging 1 or 2 percent. Not all will commence shipping on New Year's Day; some will start as late as February.

"It's bare-minimum compliance," said Kara Romanow, research director for consumer products at AMR Research in Boston, who has been surveying Wal-Mart suppliers. "They will get the tags on; the tags will have the right data. But they're not rolling out the technology throughout their product lines. They're trying to buy some time."

While some Wal-Mart suppliers, like Boston's Gillette Co., are doing extensive in-house RFID research and implementation, many others are hiring third-party subcontractors to do their tagging on the cheap, in a practice that has become known in the industry as "slap and ship." Wal-Mart is not endorsing the practice, though in their public statements, company officials profess to be patient and understanding -- at least for now.

"One thing we've tried to get suppliers to do is to look into their own enterprises," said Simon Langford, Wal-Mart's manager for global RFID strategy, who with other Wal-Mart executives has been meeting with suppliers to work out implementation schedules. "The suppliers should work out a road map about how they're going to implement this in the short, medium, and long term."