U.S. holiday sales are expected to grow as much as 3.5%, the slowest pace in six years, the National Retail Federation forecast on Tuesday, as shoppers turn more frugal and get picky with spending on non-essentials.

The largest retail trade group in the United States says it expects consumers to spend more during the upcoming holiday season but the growth in sales to be slower than last year due to concerns over persistent inflation and prices.

The National Retail Federation forecast that winter holiday spending is expected to grow between 2.5% and 3.5% on a year-over-year basis to a range of $979.5 billion and $989 billion in total holiday spending in November and December.

The National Retail Federation delivered an optimistic holiday forecast, saying it expects retail sales to grow by 2.5% to 3.5% in November and December.