Regional executives told store managers at the retailer's annual holiday planning meeting this month to rein in expenses by cutting worker hours they've added beyond those allocated to them based on sales projections.

The request has resulted in some stores trimming hours from their schedules, asking employees to leave shifts early or telling them to take longer lunches, according to more than three dozen employees from around the U.S. The reductions started in the past several weeks, even as many stores enter the busy back-to-school shopping period.

Chief Executive Officer Doug McMillon is trying to balance a desire to improve service -- partly through increased spending on his workforce -- against investors' pressure to keep profit growing. Labor costs, which rose after Wal-Mart increased its minimum wage to $9 an hour in April, have weighed on earnings, which missed analysts' expectations last quarter. At the same time, Wal-Mart is trying to maintain low prices to fend off rivals.