WASHINGTON – Joined by four moderate Republicans, Senate Democrats on Wednesday pushed through a budget amendment that would make it harder for President Bush to make permanent his $1.1 trillion in tax cuts that are due to expire by 2011.

But in a sign of how difficult it will be this year to cut spending – even in the face of record deficits – the Senate also restored nearly $7 billion in defense spending that its Budget Committee had eliminated from Bush’s proposed defense budget.

The moves came during the third day of debate over a Republican-authored $2.36 trillion budget for fiscal 2005.

Republican Sens. Olympia J. Snowe and Susan Collins of Maine, Lincoln Chaffee of Rhode Island, and John McCain of Arizona voted with the Democrats.

The Democrats said the 51-48 vote in favor of their so-called PAYGO amendment reflected mounting bipartisan fear that deficits were out of control. The federal deficit, according to the Congressional Budget Office, is expected to reach a record $477 billion this year.

The amendment, which stands for “pay-as-you-go,” would mandate that tax cuts instituted over the next five years require 60 votes to clear the 100-member Senate, unless their effect on the deficit is erased by spending cuts or tax increases elsewhere. Increases in Social Security, Medicare and other programs that entitle certain groups of people to government benefits also would require 60 votes or offsetting spending cuts and tax hikes.

In a closely divided Senate, where Republicans now hold 51 of the 100 seats, that means it would be difficult to pass new cuts.

“It means that the message of taxpayer concerns about deficits is getting through. … The Republican leadership tried very hard, twisted some arms pretty seriously to try to win it; they couldn’t win it,” said Sen. Russell D. Feingold, D-Wis., a sponsor of the amendment.

Sen. John F. Kerry of Massachusetts, the presumptive Democratic presidential nominee, took time out from campaigning to vote for the amendment, as well as another Democratic-sponsored measure that would have required 60 votes for this year’s tax cuts only; it, however, was defeated on a 52-47 vote. Kerry also voted for restoring the military spending Bush had proposed.

Democrat Zell Miller of Georgia voted with the Republicans. Democrat Tim Johnson of South Dakota, who is recovering from surgery, did not vote.

Senate Budget Committee Chairman Don Nickles, R-Okla., said that despite the first amendment’s passage, he expected three popular tax cuts due to expire at the end of this year to be extended. They are the beefed-up child tax credit, marriage-penalty relief and expansion of the 10 percent income tax bracket.

“It means we will be able to extend the bulk of what we wanted to do,” Nickles said. Once the budget is passed, Republicans – who also control the House – will have a chance to strip the amendment out of the compromise budget, which the two chambers could begin negotiating as early as next month.

And Feingold acknowledged that the Senate had sent a mixed message on spending by restoring the nearly $7 billion cut in defense funding that the Budget Committee had sought. That amendment passed by a 95-4 vote.

The White House earlier had pressured Republicans to fight to make the tax cuts permanent and to fully fund Bush’s $421 billion defense budget request.