NEW YORK (CNN/Money) - With two weeks of shopping left before Christmas, retailers are already running out of some popular holiday toys and gifts because of their own cautious expectations for the holiday season.

Worried that the sluggish economy would pinch consumer spending, retailers have kept holiday inventories taut, making it harder for them to keep the hottest toys and gifts on store shelves, some merchants and analysts said.

"I think everybody has played inventories tighter, not just ourselves, not just the play people (in the toy industry), but everybody," said Tom Alfonsi, senior vice president of merchandising for KB Toys. "We're still getting shipments and deliveries, but we're in and out of stock in the stores."

Alfonsi said inventory came in 20 percent lighter than last year. "We had planned all year to run lighter, lean and mean, and as we got closer and closer to Christmas, we felt with the economy, it was the right thing to do," he said.

Other retailers have followed similar plans.

Toys 'R' Us Inc. (TOY: down $0.20 to $12.24, Research, Estimates) said it has run short on Fur Real Friends, a toy cat that has become a top seller this year, and that Kasey the Kinderbot, another popular item, is available online but not in its stores.

Kmart Corp. said that while its inventory is in good shape, it is possible that some hot items may not be available at all stores.

"We're keeping a daily watch on inventory of course, and we're trying to address adjustments as necessary," Kmart spokeswoman Laura Mahle said.

Sears Roebuck & Co. has said it expects to have fewer clearance items after the holidays because of leaner inventories.

"There is spotty evidence that in some stores inventories are running low, but considering that the action that's in the stores is not particularly hot these days, that (low inventories) may not be the worst possible fate," said Kurt Barnard, president of Barnard's Retail Consulting Group. "In many cases a lot of stores reduced the orders they placed, and in some cases, canceled orders, which is exactly what's happening."

Merchants and vendors are paying careful attention to keeping inventories tight and cutting costs amid worries about a consumer spending slowdown. Americans have snapped up new homes and cars at a heady clip this year, lured by low interest rates and zero percent financing deals, but many of those are over and interest rates are about as low as they're going to get.

Saddled with debt, job worries and fears of a potential war with Iraq, consumers are likely to be cautious this holiday season, analysts have said. The National Retail Federation, the industry's biggest trade group, predicts a 4 percent rise in holiday sales. That's more optimistic than some forecasts, but comes in at the lower end of the group's forecasts over the past decade.

"Retailers ordered extremely conservatively for the holiday season. The shelves aren't overly abundant with goods, and controlling inventories has finally made it into broad retailers, not just Wal-Mart," said Diane Swonk, chief economist at Banc One, last week. "That's important because it means a lot of the early promotions we've seen have brought the consumers in, but has left less on the shelves with less selection."

Another issue that could be affecting holiday inventories is the 10-day West Coast port lockout in the fall, which clogged up retailers' orders for holiday merchandise. Though retailers for the most part have worked out those issues, there may be some lingering problems, said Peter Gatti, vice president for international policy at the National Industrial Transportation League, a group of cargo shippers.

"Flow is coming in now, but there's always a lag time between when the shipment occurs and when inventory can make it into the distribution chain," Gatti said.

"It's a problem particularly for retailers that source a lot of their materials through Southeast Asia and Central Asia. All that stuff goes through the West Coast. When that spigot closes, you're going to get shortages and retailers have been particularly affected by that."