By RICARDO ALONSO-ZALDIVAR

Associated Press Writer

WASHINGTON (AP) — The search for agreement on health care may be short lived.

The flashpoint is a proposal that would give Americans the option of buying medical coverage through a government plan. President Barack Obama and many Democrats have endorsed it, as one part of a broader health overhaul. On Saturday, Republicans laid down a challenge.

"I'm concerned that if the government steps in, it will eventually push out the private health care plans millions of Americans enjoy today," Rep. Roy Blunt, R-Mo., said in the Republican weekly radio address.

Blunt, who will play a leading role in the debate, warned: "This could cause your employer to simply stop offering coverage, hoping the government will pick up the slack."

The proposal he referred to would, for the first time, offer government-sponsored coverage to middle-class families, as an alternative to private health plans. By some estimates, it could reduce premiums by 20 percent or more — making it much more affordable to cover the estimated 48 million people who don't have health coverage.

It could also be a deal breaker for broad, bipartisan agreement on health care.

Insurers fear competition from a government plan could drive them out of business, and Republicans worry it would lead to a government takeover of health care. Liberals, meanwhile, are equally adamant that Americans deserve the choice of government-sponsored health care.

"The purpose of health care reform is to make sure all Americans have health care, not to promote the insurance industry," said Rep. Jan Schakowsky, D-Ill., who serves on a House panel that will help write the legislation.

The new government coverage could be similar to what seniors have in Medicare, which is run directly from Washington. Or it might be designed like the federal employee health plan, available to members of Congress, and delivered through private insurers.

Asked at the White House health care summit this week about the brewing controversy, the president promised to address the qualms felt by some. But he did not abandon the notion of a government plan.

"I'm not going to respond definitively," Obama said, answering a question from Sen. Charles Grassley, R-Iowa. "The thinking on the public option has been that it gives consumers more choices and it helps ... keep the private sector honest, because there's some competition out there.

"I recognize, though, the fear that if a public option is run through Washington, and there are incentives to try to tamp down costs ... that private insurance plans might end up feeling overwhelmed."