Prospects for health reform drop significantly when Americans hear potential financial trade-offs associated with expanding health insurance coverage, a poll indicates.

For example, nearly seven in 10 people say they favor the concept of requiring employers to provide their workers with health insurance or contribute into a fund that pays to cover the uninsured. President-elect Barack Obama has called for such an employer mandate for medium and large businesses.

But what if they heard the mandate would cause some employers to lay off workers? Support falls dramatically — to about three in 10 people, according to a new national survey conducted by the Kaiser Family Foundation and the Harvard School of Public Health.

Similarly, about two out of three people favor requiring all Americans to have health insurance. But when told some people may be required to buy insurance that’s too expensive or it’s something they don’t want, support for the individual mandate falls to 19 percent.

“As we have learned from past debates, public support looms for health reform largest at the beginning of the debate, but it’s relatively easy to chip away at that support with arguments about trade-offs,” said Mollyann Brodie, a Kaiser vice president.

Researchers said the economy is the overwhelming top concern in the United States — cited by nearly three quarters of the public. Health care is a top domestic concern too. But the survey suggests the public is split when it comes to a willingness to sacrifice financially to get more people insured.

About 47 percent were willing to pay higher insurance premiums or taxes, while 49 percent were not.

The study is based on a telephone survey of 1,628 adults conducted in early and mid-December. The margin of error was plus or minus 3 percentage points.