After months of heated battle over health care reform in the US Congress, leaders in both parties held out little hope for compromise at a bipartisan meeting that will provide a national stage for the arguments fueling the long-running debate.
"I think it's nearly impossible to imagine a scenario under which we could reach an agreement" unless Democrats scrap the reform bills passed last year, Republican leader Mitch McConnell said.
Obama and his fellow Democrats have no intention of doing that, but Obama hopes to influence wavering Democratic lawmakers and voters who have lost enthusiasm for the effort to reshape the $2.5 trillion US health care industry.
The bills passed by the Democratic-controlled House and Senate late last year were designed to rein in costs, regulate insurers and expand coverage to tens of millions of Americans.
But efforts to merge them and send a final version to Obama collapsed in January after Democrats lost their crucial 60th Senate vote in a special election in Massachusetts amid broad public dissatisfaction with the health care drive.
Obama offered his own version of the health care plan on Monday in an effort to break the legislative gridlock, but Republicans immediately rejected it. The White House still promised to seek common ground with Republicans.
"It is important to understand that this proposal isn't meant to be the final say on the legislation," said Nancy-Ann DeParle, director of the White House Office of Health Reform.
The White House has signaled it will consider backing an effort to ram the bill through Congress using a procedure called reconciliation that would bypass the need for Republican support.
Republicans said they expected the summit could be the first step in launching that process, which McConnell called "legislative sleight-of-hand." But they think Democrats have lost support for the overhaul in Congress.
"House Democrats are farther away from securing the votes to pass a government health care bill today than they have ever been," said Eric Cantor, the No. 2 House Republican.
Teams of about 20 congressional Democrats and 20 Republicans will participate in the summit, but Republicans complained it would not feature any governors. Negotiations for the summit have involved everything from the list of attendees to the shape of the table.
The meeting will be broken into sections to discuss controlling costs, insurance reforms, deficit reduction and expanding coverage.
Republicans said they would focus at the summit on promoting their own scaled-back approach to boost competition across state lines and curtail medical malpractice lawsuits.
On the eve of the summit, congressional Democrats turned up the heat on health insurers on Wednesday by attacking the industry for greed and a lack of competition.
The House voted overwhelmingly to repeal the federal antitrust exemption for health insurers and Democrats called a House hearing to blast insurer WellPoint Inc for its recent premium hikes.
Democrats called the recent premium increases for some Anthem Blue Cross customers in California a function of greed rather than need and said they highlighted the importance of reform.
"Unless Congress and the administration act, Americans across the country will continue to experience large premium increases and will be priced out of the market," said Representative Bart Stupak, head of the House Energy and Commerce oversight panel.
Americans have low expectations for Thursday's gathering, with about three-quarters of respondents in a USA TODAY/Gallup Poll believing the daylong session will end without agreement.
One in five thought they would reach a deal.
The poll found 49 percent of Americans opposed the sweeping Democratic-backed bills passed by the House and Senate, with 43 percent backing them.
