Republicans retreated Thursday and decided to postpone a Senate vote on their $2.4 trillion budget (search) until at least next month, averting a certain defeat by party moderates demanding curbs on future tax cuts.

The decision was an election-year embarrassment for both the Republicans who control Congress and President Bush. It came just hours after Bush met privately with GOP lawmakers at the Capitol and urged them to push the 2005 budget through the Senate.

The House approved the budget, a compromise between the two Republican-run chambers, on Wednesday by a 216-213 vote.

Senate Majority Leader Bill Frist (search), R-Tenn., and other Republicans expressed hope that the chamber would approve the compromise spending plan after Congress' weeklong Memorial Day recess, which begins Friday. But it was unclear when — or if — the Senate would address the measure, or perhaps a truncated version that would help it work on later tax and spending bills.

"It's premature to bring it to a vote tonight," Frist told reporters. "I don't want to shut the door by forcing people to vote when I still have other options," such as trying to persuade them to change their minds.

But that could be a tall order: Four moderate GOP senators and moderate Democrat Ben Nelson (search) of Nebraska have all resisted weeks of entreaties to support the budget, leaving GOP leaders two votes shy of passage.

Asked what might make them change their minds, one of the moderates, Sen. John McCain, R-Ariz., joked, "Some of us could get killed in tragic accidents."

The moderates, joined by Democrats, are unhappy because the plan lacks tax-cut curbs they say are merited by massive federal deficits. Those restrictions are opposed by Bush and GOP congressional leaders as roadblocks to their agenda of repeated tax cuts.

A stalemate over the issue has persisted for two months. Its continuation has overtaken earlier statements by GOP leaders that they would complete the plan on time — April 15 — to show how well they could govern.

Shy of the votes they needed, Republican leaders didn't even bring the budget to the Senate floor for debate Thursday, as they said they wanted to do.

"They control the House, Senate and White House. They just seem incapable of organizing in a way to meet about any objectives," said Sen. Byron Dorgan, D-N.D.

Republicans said they believed they could eventually prevail.

"It's democracy in action. We're just going to have to continue to work it," said Sen. Wayne Allard, R-Colo.

The budget would increase defense and anti-terror spending and hold most domestic programs level. It would also deliver a fraction of the tax cuts Bush wants — along with a near-record $367 billion deficit.

The budget sets guidelines for future tax and spending legislation and does not need the president's signature. Lawmakers can work on later measures without a budget, but they would lack its procedural advantages that would make those bills easier to pass.

In his visit with Republicans and a subsequent written statement, Bush tried intensifying the pressure by imploring the narrowly divided Senate to pass the fiscal blueprint. House-Senate bargainers put the final touches on their compromise this week.

"I urge the Senate to follow the House's lead and pass this budget so that we can continue making progress on our shared agenda of building a safer, stronger, and better America," he said.

Bush's relatively gentle cajoling contrasted with bristly statements this week that House GOP leaders have made about the maverick Senate moderates.

House Speaker Dennis Hastert, R-Ill., asked reporters if one holdout, McCain, was a Republican. And House Majority Leader Tom DeLay, R-Texas, said the moderates "need to read the Republican philosophy" of cutting taxes.

The other recalcitrant senators were Olympia Snowe and Susan Collins, both R-Maine, and Lincoln Chafee, R-R.I.

The moderates favor requiring any tax cuts or benefit increases over the next five years that worsen the deficit to be paid for with tax increases or spending cuts. That restriction could be ignored if 60 of the 100 senators voted to do so.

The compromise budget imposes the restriction only through next April 15, and exempts the only tax bill likely to become law during that period.

The budget would:

— Allow $55 billion in tax cuts next year, though only half are likely to become law because they would be exempted from Senate stalling tactics. Bush proposed $1.3 trillion in 10-year tax cuts.

— Provide the $421 billion Bush wants for defense, 7 percent over this year. There is another $50 billion for wars in Iraq and Afghanistan, of which Bush has so far requested half.

— Increase domestic security by 15 percent to $31 billion, while holding remaining domestic programs to $369 billion, $2 billion over this year.