NEW YORK (CNN/Money) - A retail industry group raised its sales forecast for all of 2004 Tuesday, although it appeared to temper its enthusiasm for the second half, which includes the crucial back-to-school and holiday shopping periods.

The National Retail Federation said it now expects retail sales to grow by 6 percent in 2004, up from its earlier estimate of a 5 percent growth.

The industry group said its revised guidance reflects stronger-than-anticipated GASF (general merchandise, apparel, sporting goods, home appliances and furniture) sales in the first half of the year.

"The economy seems to be on a much surer footing. The momentum in the general economy has translated into healthy sales for the industry," the NRF said in its most recent retail sales outlook."Total sales in the first five months of 2004 are up 9 percent . During the same period of 2003, total retail sales had increased only 5 percent."

But the industry group is wary of the second half.

"We anticipate that GASF sales gains will moderate as the economy and consumer spending slow, and yearly comparisons become more difficult," the report said.

While consumers last year benefited from lower withholding of their paychecks and the mid-year child tax credit checks, these fiscal stimuli will not be repeated this year, the NRF cautioned.

"Therefore we are counting in the improvement in the labor markets and increase in wages and salaries to provide the financial wherewithal for consumers to keep on spending. If employment growth stumbles , we could see consumer spending soften," the report said.

At least one industry watcher said he disagrees with the NRF's overall positive outlook.

"This is not the time for runaway enthusiasm. The first half was very good for retailers but consumers are going to be very wary in the second-half," said Kurt Barnard, president of Barnard Retail Consulting. He predicts retail growth of between 4.5 to 5 percent this year "if we're lucky."

Industry analysts pointed to the disappointing June comparable sales numbers last week, particularly from industry behemoths Wal-Mart and Target, as a red flag that perhaps the robust pace of consumer spending could be showing its first sign of fatigue.

Consumer spending accounts for more than two-thirds of the total U.S. gross domestic product (GDP), making it a key economic indicator.

Wal-Mart (WMT: Research, Estimates), the world's largest retailer that last year generated over $267 billion in revenue, is often considered to be a fair measure of how the American consumer spends money.

The retailer last month reported same-store sales up just 2.2 percent, at the low end of its already reduced guidance for the month. Wal-Mart. Target, the second-biggest discounter behind Wal-Mart posted sales up 2 percent in June, well below its earlier guidance for the month of a 5 to 7 percent gain.

For July, Target sees sales just 1 to 2 percent.

"There appears to be a pause in consumer spending, especially with the low-to-middle income consumers," said Bill Dreher, retail analyst with Deutsche Bank Securities. "The slowing sales also counterbalance positive economic data that show rising income and confidence levels and oil prices coming down. As far as sales go, this is a period where the consumer is taking a break."

Observers say it remains to be seen whether last month's softness is temporary or if it signal a permanent downdraft in the pace of consumer spending.

Said Barnard, "The jobs situation is still not resolved. Across several industries, inventories are rising, and we're seeing that consumers are trading down. That's an indicator that people are not beset with worries but they are turning cautious."