More Americans will lose their health insurance as the economy weakens, health care becomes more expensive and fewer employers offer coverage, the U.S. Institute of Medicine said in a report on Tuesday.

The institute, an independent research organization that advises U.S. policymakers, said safety-net services such as charity care and hospital emergency rooms cannot be relied upon to meet the needs of people without insurance.

An institute panel urged the White House and Congress to take urgent steps to ensure all Americans have coverage. The government says 45.7 million Americans, or 15 percent, had no public or private health insurance in 2007.

President Barack Obama on Monday announced a summit on health care next week and his budget director said reducing health-care costs was critical to the economy. Obama also was expected to discuss his health-care goals during his address to a joint session of Congress later on Tuesday.

"The evidence clearly shows that lack of health insurance is hazardous to one's health, and the situation is getting worse because of the erosion of employment-based health coverage due to the current economic crisis," said Lawrence Lewin, a health care consultant who led the institute panel.

The government projects the nation will spend $2.5 trillion on health care this year, compared to $912 billion in 1993.

Employer-provided insurance has been the cornerstone of private health coverage in the United States, with an estimated 160 million Americans getting their insurance this way.

SURGING COSTS

But surging health care costs are making it increasingly tough for employers to offer health insurance coverage to their workers, according to the report. And many employers have replaced permanent, full-time jobs with contract, part-time and temporary jobs without health benefits, the panel said.

Even when employers do offer health insurance, more employees are declining it because they cannot afford the premiums, the panel said. Between 1999 and 2008, the average annual employee premium contribution for family coverage rose from $1,543 to $3,354, the panel said.

"The lack of health insurance coverage for tens of millions of Americans cannot be ignored and should not be a chronic underpinning of American health care — it is in fact treatable and indeed preventable," the panel wrote.

The fiscal crunch threatens to undermine public health care programs, the panel said. With the recession and rising health costs, some states will be unable to sustain recent expansions of programs for low-income children and adults, it added.

And increases in unemployment will further fuel the decline in the number of people with employer-sponsored coverage and put additional stress on state Medicaid and children's health insurance programs, the panel of experts in health economics and policy said.

Studies show that people without health insurance wait longer to get important medical care, running up larger bills in the end.