WASHINGTON - President Barack Obama and congressional Democrats are looking ahead to a health-care showdown on the House of Representatives floor in September following a key committee's passage of sweeping overhaul legislation.

In a sign of the fight ahead, Republicans on Saturday quickly blasted the Democrats' proposals as a "dangerous and costly experiment" that will run up the federal deficit and overwhelm state budgets.

The 31-28 vote in the House Energy and Commerce Committee late Friday was weeks later than either the White House or Democratic leaders had hoped. Nonetheless, it was a triumph for them.

But it was just one step in a lengthy legislative process. The progress in the House toward providing health care to 50 million uninsured Americans was not matched in the Senate where Republican and Democratic negotiators announced they needed additional time to produce an agreement.

Overall prospects for a health bill remain uncertain. Both chambers would have to pass legislation, then work out the differences between the two versions.

The United States is the only developed nation that does not have a comprehensive national health care plan for all its citizens, and Obama campaigned on a promise to offer affordable health care to all Americans. However, the recession and a deepening budget deficit have made it difficult to win support for costly new programs.

The House committee's vote Friday came after weeks of negotiations finally satisfied concerns raised by fiscally conservative Democrats -- only to produce a compromise that riled liberals. The liberal opposition was quieted with a last-minute series of changes agreed to early Friday.

Five Democrats and all committee Republicans opposed the bill.

"We passed a bill out that shows that we can bring together conservative, moderate and progressive Democrats," Energy and Commerce Chairman Henry Waxman, a Democrat, said after the vote. "We're going to need that coalition on the House floor, and I feel confident that we'll pass a health care reform bill in the House when we come back in September."

The measure is designed to extend health insurance to millions who now lack it, at the same time it strives to slow the growth in medical costs nationwide -- Obama's twin goals.

While the pace of action was slower than party leaders had hoped, it was speedier by far than the timetable in the Senate.

There, Democrats said a deadline of Sept. 15 had been imposed on marathon talks aimed at producing a bipartisan compromise in the Senate Finance Committee.

In the Republicans' weekly radio and Internet address, Sen. John Thune of South Dakota contended that the Democrats' current proposals do not improve health care because it would force millions of Americans in employer-based coverage into a government-run system.

He also said the proposals would burden states because they expand the government's Medicaid coverage for the indigent without a clear source of funding.

Thune said Republicans would seek reforms that allow small businesses to band together to buy affordable health insurance for their employees; protect doctors and hospitals from frivolous lawsuits; encourage wellness and prevention programs proven to cut costs; and give people who buy their own insurance the same tax breaks as those who get insurance through their employers.