"I think he will answer many of the big questions about how we move forward on healthcare reform and what he considers reform to truly be."
As Obama worked on his speech, expected to last around 35 minutes, a frenzied behind-the-scenes effort to dictate the endgame of the healthcare showdown intensified on Capitol Hill and in the White House.
The president met key Democratic power brokers, House of Representatives speaker Nancy Pelosi and Senate Majority leader Harry Reid, as Congress returned from an explosive recess consumed by Republican counter-attacks.
Pelosi insisted that the creation of a government-run insurance company to compete with private health care providers -- the "public option" beloved of grass roots Democrats --- was vital to passing a bill in the House.
But with Republicans slamming the plan as evidence the government is plotting to take over the system and introduce a European-style health service, chances of passing the "public option" in the Senate appear doubtful at best.
Obama is expected to argue in favor of the government entity to compete with private insurers to help Americans who have no health coverage.
But the White House has declined to say whether he would threaten to veto legislation that did not have such an option.
Reports on Tuesday suggested growing Senate support for a system of non-profit cooperatives to replace a government-run entity.
Another possible compromise would see the public option used only in a "trigger" mechanism, to come into force if insurance firms did not live up to new requirements to broaden access to healthcare over a specified period.
Republican Senate minority leader Mitch McConnell sent a new signal that White House hopes for cooperation in passing a bipartisan healthcare bill may be in vain.
"The White House has attempted to retool its message on healthcare many times. It should be clear by now that the problem isn’t the sales pitch. The problem is what they’re selling.
"The American people are asking us to start over."
The White House categorically rejected that suggestion, arguing that work on providing health coverage to all Americans had been going on for generations and had never been so close to fruition.
Obama's rare address to Congress on Wednesday at 8 pm (0000 GMT) represents more than just a speech on healthcare.
With the young president's political brand under severe strain, the outcome of this struggle could shape his chances of passing an ambitious reform agenda and dent his authority on pressing foreign policy matters.
It comes at a time when Obama needs maximum political leverage for his effort to restore the crippled US economy, to pass global warming legislation and to answer tough questions about sending more troops to Afghanistan.
Flaming debate during August, which has seen lawmakers assailed by angry voters at town hall meetings, has contributed to a slump in Obama's own political authority.
The president's latest Gallup approval ratings stood at 51 percent on Tuesday, barely up from a low of 50 percent but down from a high of 69 percent in the euphoric early days of his presidency in February.
Should he fall below 50 percent before November, it would represent the second fastest drop of an elected president to below-majority approval since World War II, behind Bill Clinton (four months).
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