The meeting set for Tuesday afternoon comes a day after Senate Democratic leaders suggested they were ready to abandon the last vestiges of a government-run insurance program that liberals have long sought, in order to placate moderates and secure the 60 votes they need to overcome united GOP opposition.
Majority Leader Harry Reid, D-Nev., is racing to finish the sweeping bill by Christmas. There's not a vote to spare in the 60-member Democratic caucus, and Obama planned to drive the unity message home.
"President Obama will tell senators that that they've come much farther than any previous reform effort, and that the lion's share of the work is behind us," said Dan Pfeiffer, White House communications director. "He'll underscore that now is the time to come together and finish shaping legislation that will garner 60 votes and pass the Senate in short order."
"He will make it clear that the American people should not have to wait another decade or more for legislation," Pfeiffer said.
"I think what we need to hear from the president is how we get the unity in our caucus for 60 votes. We don't want a pep talk," liberal Sen. Ben Cardin, D-Md., told reporters Tuesday. "We want to see a president who will be committed to some of the concerns that many of us have without a public option - do you really have accountability on private insurance."
The White House meeting coincides with a Capitol Hill rally planned by conservative activists opposed to the bill, with speakers including talk radio host Laura Ingraham and Republican Sens. Tom Coburn and Jim DeMint.
Opponents are stepping up their criticism as Senate Democratic leaders push hard to finish the bill. To that end the Democratic leadership indicated Monday night following a senators-only meeting that it was prepared to jettison an expansion of Medicare, initially proposed as a backup to the government option.
"Put me down tonight as encouraged about the direction these talks are going," Sen. Joe Lieberman, I-Conn., said following the meeting, only 24 hours after he rattled Democrats by threatening to oppose the legislation over the Medicare provision.
Liberals had sought the Medicare expansion as a last-minute substitute for a full-blown, government-run insurance program that moderates insisted be removed from the legislation. But it drew strong opposition from Lieberman and quieter concerns from other Democrats - all of whom hold votes essential for passage.
It also drew criticism from doctors and hospitals, who are paid less to treat Medicare patients than those covered by private insurance companies.
Reid did not say flatly that Democrats had decided to drop the proposal for uninsured Americans as young as 55 to purchase coverage under Medicare, the government program now open to people when they turn 65. But several senators said it appeared inevitable.
"We're not going to get all that we want but we're going to get so much more than we have," liberal Sen. Jay Rockefeller, D-W.Va., said.
The overall measure, costing nearly $1 trillion over a decade, is designed to expand coverage with a new requirement for nearly everyone to purchase health insurance, and ban industry practices such as denying coverage on the basis of pre-existing medical conditions. Obama also has urged Congress to slow the growth in health care spending nationally; several days after Reid submitted a package of revisions, lawmakers awaited final word from the Congressional Budget Office on that point.
Disputes over abortion and the importation of prescription drugs from Canada and other countries also simmered as the Senate entered a third week of debate on the legislation.
In a gesture that Democrats said was aimed at the AARP, Reid promised that any final compromise with the House would completely close a gap in Medicare prescription drug coverage generally known as the "doughnut hole." The Senate bill goes only part way toward that goal.
Less than an hour after Reid spoke, AARP CEO A. Barry Rand issued a statement thanking the Nevada Democrat.
Sen. Byron Dorgan, D-N.D., led an effort to lift a long-standing ban on the importation of prescription drugs from Canada and elsewhere. Obama favored the plan as a senator, but the pharmaceutical industry is opposed, and the White House appeared anxious not to jeopardize a monthslong alliance with drug makers who have been helpful in trying to pass the overhaul. A vote was set for late Tuesday.
The obstacle that loomed largest was the Medicare expansion proposal, vestige of a monthslong debate over the role of government in the newly revised health care system. It emerged last week as part of a framework agreement between moderates and liberals. Additionally, the proposal called for creation of nationwide plans run by private insurance companies under the supervision of the Office of Personnel Management, which oversees health plans for members of Congress and other federal workers.
The two provisions were seen as a replacement for Reid's initial call for a government-run insurance plan to compete with private industry, a liberal priority opposed by moderates as an unwanted government intrusion. The one unrelated to Medicare is expected to survive, but without standby authority for the OPM to set up a government-run plan if no private coverage options materialize.
Associated Press writers David Espo, Donna Cassata, Andrew Miga and Ricardo Alonso-Zaldivar contributed to this report.