The nation's largest general retailers yesterday reported a moderate improvement in their September sales, although it was mainly because most people had delayed back-to-school buying because of the late Labor Day holiday.

"Generally speaking, sales were okay. I couldn't say it was a strong month," said Monroe Greenstein, a retail analyst for Bear, Stearns & Co. Inc.

This year Labor Day, the traditional end to summer, came nearly a week later than last year. That resulted in many parents delaying their school purchases from August to September, analysts said.

The later Labor Day was a boost for September sales, but it also cut into August results, said Jeffrey Edelman, an analyst with Drexel Burnham Lambert Inc. "If you look at both months together, they showed a continuation of the sluggish trend we've seen since the beginning of the year," he said.

Cooler weather in certain parts of the country also helped sales later in September, as consumers became more interested in new fall clothes, but last month's heat wave on the West Coast kept a lot of stores in that region empty, Greenstein said.

Sears Roebuck & Co., the nation's largest retailer, said its sales for the month of September were 6 percent higher than the same period a year ago. K mart Corp. reported a gain of 7.3 percent for September, and J.C. Penney Co. Inc. reported its sales increased 8.5 percent.

Wal-Mart Stores Inc., the rapidly growing discount chain, said its September sales jumped 36 percent, while its sales for the 35-week period rose 35 percent. Sales at stores open more than a year increased 13 percent in September and 12 percent for the year-to-date period.

Federated Department Stores Inc. said its sales were up 7.4 percent in September and for the year to date.

Dayton Hudson Corp. reported an 11.9 percent increase in September sales and a 13.7 percent rise in year-to-date sales. However, sales at stores open at least a year were unchanged in September and up 3 percent for the 35-week period.

May Department Stores Co. said its September sales jumped 8.7 percent and 35-week sales were 9.1 percent higher.

F.W. Woolworth Co. said its sales improved 13 percent in September and 9.3 percent over the 35 weeks, and Montgomery Ward reported an 11.7 percent rise in last month's sales and a 7.3 increase for the 35 weeks.

Jeffrey Feiner, an analyst with Merrill Lynch & Co., predicted general retailers would see a pickup in sales in the months to come as higher interest rates force some consumers to cut back on "big ticket" purchases, such as automobiles and major appliances. That would free up their money for smaller purchases, he said.

Feiner said October may be a better indication of where sales are headed as it ushers in the busy Christmas holiday buying season.

Economists keep a close eye on consumer spending, which accounts for about two-thirds of the nation's economic activity.

The figures announced yesterday cover sales of general merchandisers and specialty apparel companies and do not include the results of such retailers as supermarkets and car dealers