CHICAGO - Cash was king for U.S. consumers who shopped over the Thanksgiving weekend, according to survey results released on Sunday, and that factor could have cost retailers additional sales.

Only 26 percent of people who shopped over the weekend said they used credit cards for their purchases, according to a poll conducted for Reuters by America's Research Group.

"That's an amazing shift in consumers' habits," said Britt Beemer, founder of America's Research Group.

A total of 39 percent said they used cash, while the remaining shoppers used debit cards, the survey showed.

Consumers shunning credit cards is a bad sign for retailers, since people who buy gifts with a credit card tend to spend anywhere from 20 to 40 percent more on the gift, Beemer said.

But a greater percentage of people who said they planned to shop over the Black Friday weekend did so than usual.

Only 25.7 percent of the people who had previously said they planned to shop decided not to make purchases, the survey said.

That number was 37 percent in 2008 and 38 percent in 2007.

Data from the survey of 680 people was in line with results from the National Retail Federation which showed more traffic in stores and on websites over the Thanksgiving weekend, but less spending per person.

Retailers have slashed inventories to avoid the margin-sapping discounts they were forced to offer in 2008.

But their resolve to avoid steeper promotions may be hard to maintain as 71 percent of consumers surveyed expect prices to be lower closer to Christmas.

Almost 50 percent said that store prices were about what they expected over the weekend, with 29 percent saying prices were higher than they expected and 21 percent finding prices lower than they expected.

Separately, almost 43 percent of those surveyed said they shopped at Walmart over the weekend, a lower percentage than typical, Beemer said.

That may have been because consumers started shopping for the holidays at Walmart earlier, as a separate survey showed 65.3 percent said they have shopped for holiday gifts at the discounter at some point this year, Beemer said.