The 1,018-page initiative contains several components pushed by liberal Democrats that were long expected to be part of House legislation, but which face considerable opposition in the Senate. Most notably, the House bill creates a new public health-insurance plan aimed at individuals and small businesses that otherwise can't get affordable coverage.

The House measure would bar insurance companies from denying coverage to individuals who are sick, while also requiring most Americans to carry health insurance or pay a penalty equal to about 2.5% of their gross income. It would provide families earning up to $88,000 a year with subsidies to help them buy coverage. And it would expand health-insurance coverage through the Medicaid federal-state insurance program for the poor.

The Senate legislation is also expected to include mandates on insurers to provide coverage and individuals to carry it, although the details may differ. The bigger differences will come on the financing side, where many senators are cautious about introducing major new taxes on the wealthy to pay for health care.

The White House is pushing for action before the August recess in both houses of Congress to give lawmakers time to reconcile their two versions, pass that compromise through the House and the Senate and send Mr. Obama a final bill by autumn. The Senate Health, Education, Labor and Pensions Committee could approve its health overhaul bill as soon as Wednesday.

That will get merged with a bill in the Senate Finance Committee, where lawmakers are trying to craft a bipartisan measure. Chairman Max Baucus on Tuesday was pitching his colleagues on a plan to finance the bill through a combination of more-modest tax increases. He is trying to fill a hole of about $320 billion over 10 years, after Democrats objected to a provision to tax upper-end employee health benefits.

The fresh package included a new fee on pharmaceuticals and other health-care industries, and stiffer corporate-reporting measures aimed at collecting a greater share of corporate taxes owed each year, two Senate aides said.

Under the first proposal, health industries including drug makers and insurers would be charged an assessment, with individual companies' fees based on their market share. It's not clear how large the total assessment would be.

The proposal also seeks to raise $75 billion to $100 billion over 10 years by giving states an incentive to issue bonds that would help offset the expanded federal share of Medicaid.

"The goal here is a bunch of smaller, less controversial items that can add up," one official said.

The package may still include a modified version of the plan to tax high-end employer-provided health insurance, though on a smaller scale, aides said.

Mr. Baucus spent much of the day meeting one-on-one with members of his committee, and he put on an optimistic face. "We're going to pass very significant health reform this year," the Montana Democrat said.

But the pre-recess deadline appeared in danger as Republicans expressed concern that the process is moving too quickly.

Sen. Olympia Snowe, a key Republican whom Mr. Baucus is trying to win over, said Tuesday that the legislation is far too complex to rush and that she saw little chance of moving a bill through the Senate before the August break.

"I frankly couldn't imagine at this point bringing it to the floor and completing our deliberations...before the August recess," the Maine senator said. She said "arbitrary, artificial time frames really are not realistic given the magnitude of the task we are assigned to do."

In addition to health care, the White House also hopes for action on energy and financial-sector regulation, both of which would consume time this fall.

At a White House meeting with top Democratic leaders on Monday, Mr. Obama pushed Mr. Baucus to produce legislation by Thursday.

Senators are now talking openly of keeping the chamber in session an extra week, though some say that is simply a tactic to discourage delay by senators who have plans for vacations, congressional trips and hometown activities.

A further complication is that if it looks as if the Senate can't or won't act this summer, many House Democrats are likely to hesitate about voting on a contentious issue -- including raising taxes -- for something that might never become law.