Wal-Mart Stores Inc., the largest U.S. private employer, said it’s increasing its health-care premium for next year’s coverage by about 36% and will stop offering health-care benefits for new part-time employees working under 24 hours a week.

The change means that, for its most popular plan chosen by employees, the premium will go up to $15 per two-week pay period from $11, Wal-Mart /quotes/zigman/245476/quotes/nls/wmt WMT +0.96% spokesman Greg Rossiter said in an interview Friday. The new eligibility rule for new part-time employees doesn’t affect the company’s existing 1.4 million Walmart and Sam’s Club employees in the U.S., Rossiter said, adding the company has provided health care for part-time employees since 1996.

“The coverage we are offering hasn’t changed,” he said. “What’s changed is costs. Health-care costs are rising for everyone. Our country needs to find the way to reduce the cost of health care particularly in this economy. The current health-care system is unsustainable for everyone. Like other businesses, we’ve had to make some tough choices.”