It's beginning to look a lot like a stronger U.S. holiday sales season, with another firm raising its sales forecast, though analysts continue to believe retailers are putting margins at risk with deep discounts.

ShopperTrak, which monitors traffic at shopping malls, now expects sales in November and December combined to rise 3.7 percent, up from its September forecast of 3.0 percent.

Sales on Saturday, December 17, known as Super Saturday in the industry, totaled an estimated $26 billion, just below the $27 billion in sales tallied on Black Friday, the day after Thanksgiving, according to Craig Johnson, president of Customer Growth Partners. The estimate suggests that this past Saturday was stronger than the 2007 Super Saturday record of $25 billion, even though there is another Saturday for shoppers to buy last-minute gifts for Christmas.

This past weekend, 40 percent discounts across stores seemed to be the cost of doing business, said Nomura Equity Research analyst Paul Lejuez. This is a bad sign for margins, as promos are likely to intensify this week.

Such 40 percent promotions were seen at stores run by companies including Abercrombie & Fitch Co , American Eagle Outfitters Inc , Ann Inc Gap Inc and Wet Seal Inc , Lejuez said.

Last week, the National Retail Federation raised its forecast, calling for holiday sales to rise 3.8 percent, versus its October forecast of 2.8 percent.

(Reporting by Jessica Wohl in Chicago, additional reporting by Nivedita Bhattacharjee in Bangalore; editing by John Wallace)