A budget endorsing up to $550 billion in tax cuts through 2013 passed narrowly in the House early Friday, and seemed on its way to Senate passage with the expected support of a pivotal moderate.

Congressional Republican aides said Sen. Olympia Snowe, R-Maine, was now likely to provide the crucial vote for the $2.27 trillion budget for 2004 after getting assurances from Senate Finance Committee Chairman Charles Grassley, R-Iowa, that the final tax cut emerging from House and Senate negotiations will be no more than $350 billion.

Senate leaders began debate Friday morning confident they had just enough votes to win passage. A Snowe aide confirmed Friday that the Senator was expected to support the measure.

Snowe's vote would be the 50th for the fiscal blueprint, which would allow Vice President Dick Cheney to cast the decisive tiebreaking Senate vote.

The budget leaves final decisions on the tax cut's size to later legislation and puts Snowe and other moderates in a position where they could limit the reductions to $350 billion.

Divided mostly along party lines, the House voted 216-211 for the budget, which sets guidelines for spending and tax bills passed this year. GOP leaders had reworked it to make sure a $550 billion tax cut would be protected from a Senate filibuster.

The House voted without assurances that Senate Republican leaders can overcome concerns among their moderate members about burgeoning deficits, projected in the budget to peak at $385 billion next year and then decline gradually and disappear in 2012. The budget also raises the nation's legal debt limit nearly $1 trillion.

"We've spent money like drunken sailors," said George Voinovich, R-Ohio. "This place does not set priorities. This place does not make hard decisions. This place just continues to say 'yes' without any consideration to the next generation."

Voinovich will probably vote for the budget, aides said, but Snowe remains undecided. Other defections from the Republican camp leave GOP leaders needing Snowe and the tie-breaking ballot of Vice President Dick Cheney to adopt the budget in the Senate.

"I expect that we'll have a majority vote tomorrow," said Senate Budget Committee Chairman Don Nickles, R-Okla.

Lawmakers simultaneously negotiated an $80 billion emergency spending bill to pay for military action in Iraq and bolster homeland security. Leaders hope to complete both measures by Friday before leaving for a two-week spring recess.

The budget delivers only three-quarters of the tax cut proposed by President Bush, but congressional tax writers say they can fit the president's economic growth package -- an acceleration of income tax cuts and reduction of dividend taxes -- within the smaller framework.

"This is the best deal that we can get. It will only get worse, and we need a budget," said House Majority Leader Tom DeLay, R-Texas.

Senate moderates say any tax cut larger than $350 billion cannot pass the Senate, but the structure of the budget will give the president's staunchest tax supporters the opportunity to change their minds -- and their votes.

The version hammered out Thursday requires that the Senate's version of a tax bill be limited to $350 billion. The House can cut taxes as much as $550 billion over a decade, and the legislation produced in a House-Senate conference can match the House's target.

The rest of the budget strikes a more moderate tone than the version passed by the House. The portion of federal spending controlled by Congress can increase to $784 billion. It drops instructions that committees cut veterans benefits, health care and other automatic benefit programs to help curtail projected deficits.

Democrats said the GOP-drafted budget and its tax cuts commit future generations to paying off the cost of current debts. "This is morally irresponsible," said Ron Kind, D-Wis.

Republicans countered that tax cuts will improve the federal ledger by stimulating economic growth, and they questioned Democrats' commitment to deficit reduction. "Don't come to the floor and tell us about our big debt increase when you ask for more money," said House Budget Committee Chairman Jim Nussle, R-Iowa.

The House and Senate negotiators working on the war spending bill continued to debate whether to accept millions of dollars added in the Senate. The items included $50 million to help the U.S. shipbuilding industry and a provision helping catfish producers share in emergency farm aid approved months ago.