WASHINGTON — Retailers lost pricing power in August, as sales fell during what was seen as a heavy period of discounting in the back-to-school season, two government reports showed Friday.

Sales at apparel and accessories stores and discounters declined in August, running counter to the overall retail sales gain in the month, the U.S. Commerce Department’s monthly retail sales report showed Friday. Specialty stores posted a 0.1 percent seasonally adjusted sales decline to $19.9 billion last month compared with July, while sales at general merchandise stores, a category that includes department stores and discounters, dropped 0.3 percent to $52.4 billion. Department stores showed the only sign of strength, with sales rising 0.1 percent to $15.3 billion in the month.

In the overall economy, retail sales rose 0.9 percent to $406.7 billion.

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“Consumers and retail companies continue to face many questions and challenges, from stubbornly high unemployment and stagnant incomes to depressed housing prices and the looming fiscal cliff all playing into overall economic uncertainty and declining consumer confidence,” said Matthew Shay, president and chief executive officer of the National Retail Federation. “Adding to this anxiety, retailers are now preparing for a potential labor disruption at the East and Gulf Coast ports, which may interfere with the all-important holiday shopping season.”

Shay said the NRF, along with other business groups and politicians, has been pressing both sides to continue their negotiations until the Sept. 30 deadline and beyond, if needed. Many have put contingency plans in place. The East Coast dockworkers’ contract expires at the end of this month, while West Coast longshoreman have been operating without a contract for more than a year.

“The last thing this economy needs right now is a work stoppage at the ports,” Shay said.

Kevin Regan, senior managing director at FTI Consulting, said: “I think it [the decline in sales] is simply pointing to the fact that momentum is slowing, and I think that retailers are seeing that and being cautious as they go into the holiday season….My suspicion is that consumers are continuing to be very surgical in what they do. They are buying more on a needs basis.”

Regan said retailers are going to get through the year by managing their expenses, payrolls and inventories.

“Generally it seems that consumers are pulling back,” said Jeet Dutta, senior economist at Moody’s Analytics. “If consumer confidence does not improve meaningfully, and there is a tendency toward discounts, then sales [declines] among retailers will continue.”

He called the retail sales data “weak,” although there was a strong headline number driven primarily by higher gasoline prices.

The Consumer Price index, also released by the Commerce Department on Friday and a key gauge of inflation in the U.S. economy, showed apparel prices fell 0.5 percent in August. Women’s apparel prices declined a seasonally adjusted 0.7 percent, while men’s apparel prices dipped 0.2 percent.

The overall CPI rose 0.6 percent in August, following a flat reading in July. Core prices, excluding volatile food and energy prices, were up 0.1 percent.

Dutta attributed the decline in apparel retail prices primarily to falling input costs, notably the steep drop in cotton prices compared to a year ago.

“It seems like that drop in input prices is finally being passed along to the consumer,” he said.