Major retailers including Target Corp., J.C. Penney Co. and Best Buy Co. are cranking up promotions to avoid a slump after Black Friday and keep customers shopping through what promises to be a difficult season.

The weak economy and growing clout of online sellers is upending carefully calculated promotions and positioning retailers' Web sites as the frontline in this year's competition.

Amazon.com Inc. joined the fray with a "Black Friday Deals Week" which began Monday with a host of limited-time deals. Executives at the largest online retailer by revenue also promised to scour competitors' Black Friday store specials and meet or beat their prices.

"You can get great Black Friday deals on Thanksgiving Day and on Black Friday on Amazon," said Paul Ryder, Amazon's vice president of consumer electronics, adding, "When it is three in the morning and you are thinking about getting up" to join a Black Friday queue at a store, Amazon hopes users go online.

The competition for Web shoppers accelerated this week when most major retailers began Black Friday-style sales online, betting that many would rather click for deals on Thanksgiving than wake up before dawn and head to stores in search of door-busters the following day.

"Extending the length of the promotional season makes perfect sense, because when you look at what people buy in these early door-buster sales, it's usually something for themselves," said Paul Leinwand, a vice president in the retail practice at consultancy Booz & Co. "There is a lot of pent-up demand for personal purchases right now. It doesn't compete with the gift shopping, which comes later."

The proliferation of online specials before Black Friday, which also included special one-day deals from Wal-Mart Stores Inc., underscores retailers' anxiety at forecasts this holiday season could be the second year in a row of declining sales. Polls of retailers also indicate more are advancing promotions once scheduled for late December.

By Thanksgiving, dozens of retailers were dangling special offers on their Web sites, though not all were identical to what could be found Friday in stores.

Target kicked off a special Thanksgiving Day sale online this year for the first time, trumpeting, "The dishes can wait. The deals can't." It was selling the latest 32-gigabyte version of the iPod Touch for $269.99, $30 cheaper than Apple Inc.'s online store. The one-day deals were separate from a promotion the retailer was planning to begin Friday.

Clothing chain J.Crew Group Inc. was boasting, "No crowds. No lines. No hassles." in an e-mail to customers promoting its early sale, while Pottery Barn Kids also touted "Black Friday Savings" in a one-day sale Thursday that was set to expire at midnight.

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