Shoppers also showed signs they will do more of their spending after December 25 than they did in the same period last year in the hopes of snagging even more deals.

Analytics firm RetailNext estimated on Sunday that U.S. retail sales fell by a mid-single-digit percentage at brick-and-mortar stores on Friday and Saturday, two of the four most important shopping days of the season, compared with the same days last year.

That does not include online sales, which have been strong.

The number of visits to stores fell 7 percent on Friday and Saturday, RetailNext said.

"Retailers recognize that consumers will wait as long as they need to," said Charles O'Shea, senior analyst at Moody's Investors Service.

Only two-thirds of Americans are all or almost finished with their Christmas shopping, according to a survey by consumer research firm America's Research Group and Inmar.

Of those not finished shopping, consumers holding out for bigger bargains is up 25.1 percent from 20.8 percent last year, the firm said.

Analysts have said this is turning out to be the most competitive holiday season since the recession, forcing retailers to ramp up promotions. The season generates 30 percent of sales and 40 percent of profits for many stores.

Major retailers significantly ramped up the frequency of their promotions in the first part of December, according to data prepared for Reuters by Market Track, a firm that provides market research for top retailers and manufacturers.

HOLDING OUT FOR BARGAINS

"I'm doing my shopping on a budget, which is why I'm digging through the clearance bin," said Katrina Attis, 25, as she shopped on Sunday at a J.C. Penney Co Inc store in a mall in Elmhurst, New York.

Before Christmas, Attis will focus on her immediate family. For herself and other members of her family, she will shop next week when she expects bigger bargains.

O'Shea, who noted bigger discounts this weekend than in the corresponding weekend in 2012 as he did store checks in various cities, said the problem was particularly acute for specialty apparel retailers.

He cited teen apparel chain Abercrombie & Fitch as one of the stores with the most noticeable increases in price cuts.

Rival Aeropostale Inc, which is trying to stanch deep sales declines, was touting up to 70 percent off everything in its stores on Sunday.

While electronics chains have benefited from best-selling items like Microsoft Corp's Xbox One video-game console and Sony Corp's rival product PlayStation 4, clothing has been a harder sell, he said.

No. 3 U.S. retailer Target Corp suffered reduced customer traffic over the busiest shopping weekends of the year in the wake of a massive data breach, retail consultancy Customer Growth Partners LLC said.

Hackers stole data from up to 40 million credit and debit cards of shoppers who visited Target stores during the first three weeks of the holiday season in the second-largest such breach reported by a U.S. retailer.

The number of transactions at Target on Saturday was down by less than 5 percent compared to the same period a year ago, Customer Growth Partners estimated.

Britt Beemer, the chief executive of America's Research Group, said Target weathered the security breach "amazingly well," as it saved face by offering customers an additional 10 percent off on purchases over the past weekend.

SOME CHEER

Still, some retailers seem to be faring well. Chad Hastings, the general manager of Town East Mall in Mesquite, Texas, said the department stores in his mall told him sales this weekend were better than expected. The mall is anchored by Penney, Macy's Inc, Dillard's Inc and Sears.

"We expect the next two weeks to pick up a lot of the slack," Topeka Capital Markets analyst Dorothy Lakner wrote in a note on Monday.

Lakner said she expects Tiffany & Co, Fossil Group Inc and apparel retailers Lululemon Athletica Inc and Zumiez Inc to do better than others.

"With compelling new collections like Ziegfeld, some old favorites like Keys in resurgence and hot trends such as colored diamonds, not to mention benefits from lower raw materials prices, we think (Tiffany) should be a standout for holiday."

The analyst also said Fossil stands to benefit as it has a strong portfolio of watch brands, which include Michael Kors, Marc Jacobs and Burberry.

Store checks showed Lululemon showed continued popularity amongst its core female customers while the colder weather has helped Zumiez, Lakner said. The company sells snowboards and winter sportswear.

Retailers caught a break from Mother Nature. Despite a winter storm that hit major Midwestern markets such as Chicago and Detroit, no event was severe enough to disrupt holiday shopping in any part of the country, said Evan Gold, a senior vice president at Planalytics, a weather consulting firm in Berwyn, Pennsylvania.

Gold predicted no disruptions in the last two days before Christmas.

Experts expect the promotions to continue until the very end of the season in January.

"Without question, the shopper is in the driver's seat," said John Yozzo, a managing director at FTI Consulting in New York.

(Additional reporting by Siddharth Cavale; Editing by Jan Paschal, Joyjeet Das and Saumyadeb Chakrabarty)

By Phil Wahba