WASHINGTON — The health insurance industry said Wednesday it will support a national health care overhaul that requires them to accept all customers, regardless of pre-existing medical conditions, but in return it wants lawmakers to mandate that everyone buy coverage.

Lawmakers have signaled their intent to craft health care legislation early next year, and the insurance industry's support would make passage easier. That legislation is expected to closely track the proposals of president-elect Barack Obama. However, Obama separated himself from his Democratic challengers by opposing an individual mandate for adults to buy health insurance.

More lawmakers may agree to a mandate if it means the insurance industry will back those efforts. They'll remember it was the industry's opposition 15 years ago that helped scuttle former President Clinton's health plan.

The board of directors for America's Health Insurance Plans agreed to the trade-off Monday night. The board endorsed the proposal after a series of hearings in various states.

"We hope this will be a contribution to help members of Congress fashion their proposal," said Karen Ignagni, president and chief executive officer of the trade group. "We're going to provide all the technical background that we have assembled, all the experience we've assembled at the state level, and we're going to work very hard with members of Congress on both sides of the aisle. We want to make sure that whatever reforms are advanced, no one falls through the cracks."

Obama's health plan calls for a health insurance exchange, a sort of government-run shopping center where customers could go to select from private plans or a plan administered by the federal government. Any insurer that wants to participate in that exchange must accept all customers regardless of pre-existing health conditions, such as diabetes or heart disease.

Insurers will want to participate in the exchange because government subsidies will make it easier for millions of people to buy coverage from them. But the insurers say that experience in the states shows the coverage guarantee often made it harder for people to find coverage. That's because insurers raised premiums to meet the expense of covering all applicants with chronic health conditions.

"They ended up making the problem much worse," Ignagni said of the state efforts. "The data is clear about the need to have everyone part of the system."

Analysts say Massachusetts is an example where the coverage guarantee has worked well, but it's also a state that requires everyone to buy health coverage or suffer a tax penalty.

Some key Democratic lawmakers have already expressed support for an individual mandate. The concept was a centerpiece of Sen. Hillary Rodham Clinton's health care plan. It was also part of the blueprint offered last week by Sen. Max Baucus, chairman of the Senate Finance Committee.