Most employers plan to lower their health care costs next year by tapping a familiar source of help: their workers.

Preliminary findings released this week from an employer survey by consulting firm Mercer Inc. show that 59 percent of U.S. employers will reduce their health costs in 2009 by increasing workers’ deductibles, co-pays and percentages of a medical bill that workers pay.

Even with shifting costs to workers, U.S. employers still project a 5.7 percent increase in health benefits cost next year, according to the Mercer survey of 1,317 employers. That increase is lower than those of the previous 10 years but still higher than the general rate of inflation. Small businesses will face 10 percent increases.

The annual rise in benefit costs stems, in part, from the continuing increase in prices of medical services and of prescription drugs. And more medical services are being used per person, Holmes said.

Many employers have more moderate benefit increases than previous years, in part because they’re focusing on health care as a mounting threat to profitability. “CEOs have put the cost of health care as one of their top business priorities,” Holmes said. Businesses are increasingly promoting wellness programs and installing high-deductible health plans, which lower their costs.