Scheduling of the speech next Wednesday night, just a day after lawmakers return from their August recess, underscores the determination of the White House to confront critics of Obama's overhaul proposals and to buck up supporters who have been thrown on the defensive. Allies have been urging the president to be more specific about his plans and to take a greater role in the debate, and aides have signaled he will do that in the address to a joint session of Congress in the House chamber.
The speech's timing also suggests that top Democrats have all but given up hope for a bipartisan breakthrough by Senate Finance Committee negotiators. The White House had given those six lawmakers until Sept. 15 to draft a plan, but next week's speech comes well ahead of that deadline.
It follows an August recess in which critics of Obama's health proposals dominated many public forums. Approval ratings for Obama, and for his health care proposals, dropped during the month.
White House senior adviser David Axelrod told reporters Wednesday, "We believe this is the best way to kick off the final discussions, the final debate, and bring this thing to a close in a way that is meaningful."
Listeners to Obama's speech will have "a clear sense of what he proposes and what health care reform is not," Axelrod said. He declined to offer details of what the president might discuss.
Axelrod said earlier that all the key ideas for revising health care are "on the table," suggesting that Obama will not offer major new proposals.
But he may talk more specifically about his top priorities, and perhaps add details to pending plans, to save a high-profile initiative whose defeat would deliver a huge blow to his young presidency.
Many advocates of sweeping health care changes - which would include health coverage for virtually every American, greater competition among insurers and incentives to increase the quality of care instead of the number of medical procedures performed - welcomed the president's more direct role. Obama and congressional Democrats clearly lost momentum during the August recess, they say, and the president's high profile and still-considerable personal popularity are needed to change the dynamic.
"He's got to get into the nitty-gritty and embrace very concrete proposals," said Ralph Neas, head of the National Coalition on Health Care.
Richard Kirsch, national campaign manager for the liberal advocacy group Health Care for America Now, said, "It's really clear they understand they have to provide more presidential leadership, more presidential direction."
Kirsch said Obama doesn't have to provide legislative language, but he must detail "the contours of the reform he needs."
It's far from clear that Obama's speech will satisfy grumbling liberals. For instance, he consistently has refused to insist on a government-run program to compete with private health insurers, a top goal of liberals, even though he says he prefers such an option.
Axelrod called the public option important, but stopped short of saying it was essential to a final bill.
Several lawmakers say Obama must convincingly show that he can reduce the cost of pending health care plans. Nonpartisan budget officials have said Obama's proposals could increase the federal deficit by about $1 trillion over the next decade.
Neas said billions of dollars can be saved by changing health payment practices to discourage unnecessary procedures. He also said insurance and pharmaceutical companies should be required to offer more savings to the nation's health care system because they will benefit from millions of new customers if greater coverage of Americans is mandated.
Such demands could be awkward for Obama. He has praised those industries for the cost reductions - worth tens of billions of dollars over the next decade - they already have pledged to make.
Before Obama's speech to Congress was announced, the Republicans' top negotiator on health care indicated Wednesday that bipartisan talks would continue despite White House suggestions that he and another GOP bargainer have not acted in good faith.
Jill Kozeny, a spokeswoman for Sen. Charles Grassley of Iowa, said the accusations were unjustified. She said Grassley and the five other Senate Finance Committee members - half Republicans, half Democrats - will hold their scheduled conference call Friday to try again to reach common ground on a health care bill that could win broad support in the full Senate.
Axelrod on Tuesday suggested that Grassley and Sen. Mike Enzi, R-Wyo., have not acted in good faith because they sharply criticized Democratic plans during the August recess.
Kozeny said Wednesday: "Attacks by political operatives in the White House undermine bipartisan efforts and drive senators away from the table."
Enzi spokeswoman Elly Pickett said of her boss: "Repeating that you don't agree with plans put together solely by one side doesn't mean you aren't willing to work together on a different plan. He is."
Axelrod had kind words for the third GOP Senate negotiator, Olympia Snowe of Maine. Many lawmakers see her as the likeliest possible Republican senator to support a major health care package if a true bipartisan accord can't be reached.
Obama "has a high regard for her," Axelrod said. "She's made a good faith effort to try and find common ground."
In one measure of the intense opposition Obama and his allies faced this summer, opponents of the Democratic effort outspent supporters on television commercials in August for the first time this year, according to a firm that monitors political advertising.
Foes of the Democratic drive spent $12.1 million last month, compared with $9.1 million for backers of the effort, according to Evan Tracey, president of the Campaign Media Analysis Group in Arlington, Va. The U.S. Chamber of Commerce and several conservative groups were the biggest advertisers against the health care overhaul, while the drug industry, labor and AARP spent the most on the effort's behalf.
Republicans and groups opposed to Democratic health care proposals have vowed to keep up the fight. A few hours before the president's speech on Wednesday, activists will present lawmakers with stacks of petitions opposing "government-run health care." The event is sponsored by the conservative National Center for Policy Analysis and Salem Radio Network.