NEW YORK — The outlook for the back-to-school shopping season seemed grim yesterday, as retailers' July sales reports showed an increasing shift toward buying necessities like food and household supplies at discounters and away from discretionary spending on clothing.

With the benefits of the government stimulus checks fading and jobless claims at a six-year high, the big worry is how much shoppers — squeezed by high gas and food prices — will retrench in the critical months ahead.

Wal-Mart Stores Inc., the world's largest retailer, and Costco Wholesale Corp. posted solid gains. But July results for Wal-Mart fell slightly short of Wall Street forecasts. The company noted that shoppers are increasingly running out of money and projected that sales would slow in August as the benefits from the stimulus checks dry up.

Costco's outlet in Iwilei, one of six it has in Hawai'i, is the chain's top-selling store in the U.S., according to company officials.

Meanwhile, many mall-based apparel stores including Limited Brands Inc. and Gap Inc. suffered even deeper declines. Luxury stores like Saks Inc., which operates Saks Fifth Avenue, also struggled with weaker sales as even affluent shoppers pull back.

"Consumers are in a fair amount of pain," said Ken Perkins, president of research company RetailMetrics LLC. He worries that without the government stimulus money, shoppers won't have any incentive to splurge on back-to-school merchandise.

"This is going to be a very promotional, challenging back-to-school season," he added.

The International Council of Shopping Centers-UBS sales tally of 38 stores reported a 2.6 percent increase in July, in line with the 2.5 percent pace seen since the beginning of the industry's fiscal year, which starts in February. The tally is based on same-store sales — those at stores open at least a year — and are a key indicator of a retailer's health.

July's results met ICSC's projections for a 2 percent to 3 percent gain, but the pace was much slower than the 4.2 percent gain in June, which was helped by a boost from the stimulus checks. But ICSC's chief economist Michael P. Niemira said that the July sales saw a wider gap between low-price operators and mall-based apparel stores.

"You're definitely seeing a broader pullback on discretionary items," said Niemira.

July is among the least important months of the year for retailers since stores are clearing out summer goods to make room for back-to-school merchandise. So analysts will pay closer to attention to August and September to gauge the fall selling period.

Still, the July figures do provide a glimpse of shoppers' willingness to spend. The good news is that despite July's sluggish sales, there wasn't a flurry of second-quarter downward revisions by merchants, meaning that the industry is keeping its inventories under control.

Still, as major retailers such as Wal-Mart report their earnings starting next week, the results are expected to show that customers are finding that their paychecks are not keeping up with rising food and gas prices.

Shoppers are also dealing with tighter credit, a housing slump that doesn't look like it will be ending anytime soon and a weaker job market. Such fears have dragged down consumers' outlook for the economy to the lowest level in decades, according to the Conference Board.

Yesterday's report on unemployment underscored the woes in the job market. The Labor Department reported that the number of newly laid-off people signing up for benefits rose by a seasonally adjusted 7,000 to 455,000 for the week ending Aug. 2 — putting claims at their highest level since late March 2002.

Facing these increasing financial worries, Americans have been shopping at lower-price alternatives — which has helped stores like Wal-Mart and Costco. But yesterday's sales reports show that even discounters, which had been the biggest beneficiaries of the stimulus checks in recent months, are facing tougher times.

Wal-Mart reported a 3 percent gain in same-store sales for July, missing the 3.4 percent gain expected by analysts polled by Thomson Financial. The company has predicted a modest same-store sales gain of 1 percent to 2 percent for August.

The discounter said its home and apparel business posted declines but noted sales momentum in back-to-school offerings, which it expects will continue through August.

"With the end of the stimulus checks, we know consumers are spending more cautiously, and we continue to see a pronounced paycheck cycle at the end of the month," Eduardo Castro-Wright, president of Wal-Mart's U.S division, said in a statement.