MasterCard Advisors SpendingPulse said sales in the two months before Christmas increased 0.7 percent, compared with last year. Sales grew at a 2 percent pace in the same period a year ago. SpendingPulse tracks total U.S. sales at stores and online via all payment forms.

Michael McNamara, a SpendingPulse vice president, told Bloomberg News that Americans became concerned about the fiscal cliff towards the end of the selling period. Hurricane Sandy also interrupted shopping in stores and online after it slammed into the East Coast in late October.

You are looking at modest to marginal growth from a year ago, said McNamara. Weather events and the fiscal debate both anchored the season in terms of growth. The media coverage, which did a good job of explaining the negative consequences of the fiscal cliff, created this negative trend in consumer confidence and spending.

The results were weakest in areas affected by Sandy and a more recent winter storm in the Midwest. Sales declined by 3.9 percent in the mid-Atlantic and 1.4 percent in the Northeast compared with last year. They rose 0.9 percent in the north central part of the country. The West and South posted gains of between 2 percent and 3 percent.

Online sales, typically a bright spot, grew only 8.4 percent from Oct. 28 through Saturday, according to SpendingPulse. That’s a dramatic slowdown from the online sales growth of 15 to 17 percent seen in the prior 18-month period, according to the data service. The estimate contradicted a report by ComScore, which estimated Dec. 23 that online retail sales increased 16 percent from Nov. 1 to Dec. 21 compared with the same 51-day period a year earlier.

The SpendingPulse data include sales by retailers in key holiday spending categories such as electronics, clothing, jewelry, luxury goods, furniture and other home goods between Oct. 28 and Dec. 24. They include sales across all payment methods, including cards, cash and checks.