Thanksgiving traditionally has been a day to pause, eat turkey, kick back and watch football. But this year, an increasing number of retailers are promoting bargains on Thanksgiving to entice overstuffed shoppers off their overstuffed sofas and into their stores.

Retailers including Walmart Stores Inc., Sears Holdings Corp., Toys “R” Us Inc. and Gap Inc. will open most of their outlets on Thanksgiving day to get a jump on the holiday shopping season, which officially kicks off on Black Friday.

Experts say the early day strategy underscores the pressure retailers face to draw customers during the holiday season after several years of scaled-back spending during the recession.

It’s a strategy that appears to be gaining momentum.

Last year, 18 million shoppers hit the stores on Thanksgiving day, up from 11 million in 2007, according to the National Retail Federation.

Still, holiday shopping on Thanksgiving can be a tough sell without the proper motivation, said NRF spokeswoman Kathy Grannis.

“Obviously, the deals have to be attractive enough to get people out of their homes and away from the pumpkin pie,’’ she said.

Grannis said shoppers can expect to find deep discounts on Thanksgiving but nothing like the predawn retail deals that will be available Friday.

“Opening on Thanksgiving is a way to offer discounts and added convenience for those shoppers who want to beat the madding crowds on Black Friday, but you won’t see the type of deals on Thanksgiving that you’ll see the next morning,’’ she said.

That’s because Black Friday is still the Super Bowl of holiday shopping, and the throngs of shoppers descending on stores and shopping malls offer retailers the best opportunity to maximize profits.