In a reach across party lines, the Senate overwhelmingly passed sweeping legislation Wednesday to prevent a Jan. 1 income tax increase for millions and renew jobless benefits for the long-term unemployed.

The 81-19 roll call cleared the way for a suspenseful vote in the House on Thursday, where rebellious liberals announced plans to try and stiffen an estate tax provision they oppose as too generous to the rich.

President Barack Obama quickly told reporters he wants the bill passed unchanged, so it can reach his desk quickly for a signature. And Senate Republicans have warned any modification could doom the bill's prospects for passage in time to head off the tax hikes.

"I know there are different aspects of this plan to which members of Congress, on both sides of the aisle, object," Obama said. "That's the nature of compromise. But we worked hard to negotiate an agreement that's a win for middle-class families and a win for our economy. And we can't afford to let it fall victim to either delay or defeat."

But House Democrats argued their proposed change would shave $23 billion off the cost of the bill and ease the impact on deficits. "It doesn't create jobs, it adds to the deficit," Rep. Chris Van Hollen, D-Md., said of the more generous estate tax included in the bill. "Is that the message this Congress wants to send at a time of high deficits?"

At its core, the legislation provides a two-year extension of the tax cuts at all income levels that Congress approved while George W. Bush was president. Without action, they will expire on Dec. 31.

The bill also would cut 2011 Social Security taxes for all wage earners, a reduction that will mean an extra $1,000 in take home pay for an individual earning $50,000.

In addition, the legislation renews a program of jobless benefits for millions who were laid off more than six months ago. Officials said that without the bill, government checks will be cut off for two million Americans over the holidays, and millions more over the next year.

Energy tax provisions, including extension of a government subsidy for ethanol and breaks for producers of other alternatives to oil, were added in recent days to strengthen lawmakers' support for the measure.

The legislation amounted to the first fruits of a new era of divided government, a deal sealed little more than a week ago by Obama, who is nursing a fragile economic recovery midway through his term, and Republicans whose position was greatly strengthened in last month's elections.

Concessions made by the president sparked criticism from liberals who were angered at tax cuts for the wealthy that he had long criticized. Some provisions agreed to by Republican leaders brought objections from conservatives unhappy that the cost of the jobless benefits would swell the federal budget deficit.

And in the hours before final passage, lawmakers on both sides maneuvered for political gain, a sign of renewed struggle in 2011.

A Democratic attempt to ease the paperwork burden imposed by this year's big health care bill was blocked by Republicans. Democrats countered by vetoing a GOP alternative that would have included offsetting spending cuts.

In the end, though, the tax bill drew support from 44 Democrats and 37 Republicans, testament to the appeal of lower taxes and renewal of a program of aid for victims of the recession at a time of 9.8 percent unemployment. Fourteen Democrats and five Republicans voted against the bill.

Obama's call for the House to accept the Senate-passed measure continued a postelection season of contentiousness between the president and Democrats distressed that they lost their majority in November.

For Democratic House leaders, the dilemma was evident — trying to keep faith with members of the rank and file who want to change the legislation, yet avoid at all costs having Democrats saddled with blame if taxes increase on Jan. 1.

That's what the Senate Republican leader, Sen. Mitch McConnell of Kentucky, warned might happen if the bill was changed.

"This agreement is not subject to being reopened," he said on Tuesday. "In other words, we have an understanding."

However, McConnell's insistence didn't extend to a series of Republican attempts to make modifications in the moments before Senate passage.

He and other Republicans sided with a failed attempt by Sen. Jim DeMint, R-S.C. to make the tax cuts permanent, and again when Sen. Tom Coburn, R-Okla., unsuccessfully proposed spending cuts to cover the cost of the unemployment benefits.

In the House, Obama's liberal critics were outspoken.

A closed-door meeting of the rank and file ended inconclusively Tuesday night, and afterward Rep. David Wu, accused the president of showing weakness in the face of an emboldened Republican Party.

"He has no street cred," the Oregon Democrat told reporters. "This tax bill is a thin part of the problem. They're going to get eaten alive by the Republicans in this chamber," he added, referring to White House officials.

By far the most controversial element of the bill concerned the estate tax. Under the measure, individual estates as large as $5 million would pass to heirs tax free — an amount that would reach $10 million for couples — with the balance taxed at a rate of 35 percent.

Under the Bush-era tax cuts, the estate tax was repealed for 2010, but scheduled to return on Jan. 1 with a top rate of 55 percent on the portion of estates above $1 million — $2 million for couples.

Unhappy with the more generous approach that Obama agreed to, House Democrats voted in a closed-door meeting last week they would not permit the legislation to reach the floor without changes.

They have since retreated from their ultimatum, and now hope they can change the measure on the floor to restore the tax to levels in effect in 2009. At the time, individuals could pass $3.5 million to their heirs, tax-free. Couples could pass $7 million, with a little tax planning, and the balance was taxed at a top rate of 45 percent.