WASHINGTON — Key House Democrats decided Friday to raise taxes on the wealthy to help pay for health care legislation, at the same time they sought to quell concerns among moderate and conservative lawmakers about other elements of the bill atop President Barack Obama's domestic agenda.

The decision, made behind closed doors, capped an up-and-down week as Obama, traveling overseas, reflected that "We're closer to that significant reform than at any time in recent history. That doesn't make it easy. It's hard."

A new surtax agreed to by Democrats on the tax-writing Ways and Means Committee would start with households making $350,000 a year and begin in 2011, said the committee's chairman, Rep. Charles Rangel, D-N.Y.

It would raise some $540 billion over 10 years, about half the cost of Obama's ambitious plan to reshape the nation's health care system and provide care to the 50 million uninsured.

But the proposal faces an uncertain reception in the Senate and from moderate and conservative Democrats in the House, who rebelled Thursday over various aspects — including costs — of the plan.

Democratic leaders spent hours Friday trying to soothe those concerns without reaching resolution, even as Rangel's panel met to come up with a payment proposal.

Obama acknowledged obstacles to the legislative timetable but said failure to meet a self-imposed August deadline for moving bills through the House and Senate didn't doom the endeavor.

"I never believe anything is do-or-die," the president said at a news conference in Italy. "But I really want to get it done by the August recess."

Rangel said the new surtax would be graduated, starting with households at $350,000 and then rising at $500,000 and again at $1 million. In combination with cuts to Medicare and Medicaid and fees paid by employers who don't provide insurance to their employers, that would pay for a comprehensive health bill costing around $1 trillion over 10 years.

"Instead of putting pieces of different revenue raisers together the best we can do is a graduated surtax," Rangel said.

Rangel didn't describe details, but one official said the surtax would apply to individuals with adjusted gross incomes over $280,000 a year, and couples over $350,000. A senior House aide said the surtax would be 1 percent for the first group of high earners, those households making $350,000 or more. The levels for the other two groups, those above $500,000 and $1 million in annual income are still being determined, said the aide.

Both officials spoke on condition of anonymity to discuss private deliberations.

House Democrats had hoped to release a final bill Friday, but that was before a group of moderate and conservatives, known as Blue Dog Democrats, voiced their objections. House leaders are now promising a bill Monday with committee votes later in the week.

Associated Press writers David Espo and Ricardo Alonso-Zaldivar contributed to this report.