Senate passage of a massive economic stimulus bill likely rests on an amendment cutting as much as $50 billion from the $900 billion-plus measure.

Yet even if Senators take an ax to the bill, Democrats and Republicans alike acknowledged Wednesday that the final vote will be a squeaker, instead of the comfortable bipartisan majority that President Barack Obama has so aggressively sought.

Lawmakers in both parties continue to have heartburn over spending such a large amount of money, particularly on items such as insurance for honeybee farms and State Department diplomatic programs.

To get the 60 votes needed to overcome procedural hurdles and a possible GOP filibuster, Senate Democratic leaders are scrambling to find the cuts to programs that would not provide a short-term jolt to the economy. However, aides warned the amount to be stricken could range higher or lower than the $50 billion mark, depending on which programs are targeted.

“The key is what can we cut to satisfy whatever wavering Democrats we’ve got and pull in a few” Republicans, one senior Senate Democratic source said.

Senate Majority Leader Harry Reid (D-Nev.) still hopes to finish the package this week and is prepared to keep the Senate working through the weekend if necessary, spokesman Jim Manley said.

“The need for action on an economic package only grows with the passage of time, and Sen. Reid is determined to do whatever he can to get the votes necessary to pass a recovery plan,” Manley said.

Yet as of Wednesday evening, Reid still did not appear to have the 60 votes, Democrats acknowledged.

“If the final vote was now, it would not pass,” a senior Senate Democratic aide said. “But we’re not done fixing it yet.”

Still, the staffer said an ailing Sen. Edward Kennedy (D-Mass.), who has not voted since he suffered a seizure on Inauguration Day, would probably need to come back for the vote. Democrats have just 58 Members in their Conference, meaning Reid will need all of his rank and file and at least two Republicans to ensure passage.

Senate Majority Whip Dick Durbin (D-Ill.) said he is convinced that all Senate Democrats will ultimately support the measure, but only after it has been tweaked to allay their concerns.

“I think that all the Democratic Senators are looking for a way to support this with a very constructive approach. I hope at the end of the day we have their support. I believe we will,” Durbin said.

Making the bill acceptable to the Conference appears to depend on an amendment to strip funding for programs that have been ridiculed by Republicans and Democrats alike in recent days.

Senate Democratic leaders had been content to let moderate Sens. Ben Nelson (D-Neb.) and Susan Collins (R-Maine) draft the proposed cuts, but are worried that some GOP lawmakers involved in the effort also want to target funding for education programs.

To guard against having a troublesome vote for their own, Democratic leaders were working on a contingency plan — a separate amendment in case the Nelson-Collins plan becomes unpalatable to the rank and file.

Durbin didn’t mention the leadership-driven proposal but said he hopes Nelson’s plan will attract broad support.

“He’s working in good faith, and we’re working with him in the hopes that we can get general support for the amendment on both sides,” Durbin said.

A Nelson spokesman said the amendment — which was still being negotiated as of press time — would cut more than $50 billion from the bill and would likely strike programs such as $61 million for State Department diplomatic and consular programs, $122 million for new and renovated Coast Guard polar ice breakers, and $198 million for Filipino veterans.

In addition to cutting billions from the measure, Democratic leaders also hope to attract some GOP support by adopting a proposal by Sen. Johnny Isakson (R-Ga.) to expand a tax credit for homebuyers. The Senate was expected to vote on the Isakson proposal Wednesday night.

Obama met with Nelson, Collins and a third moderate, Sen. Olympia Snowe (R-Maine), on Wednesday to gauge what changes to the bill they were seeking.

“The White House is trying to lock in some of the moderate people and trying to find out what they want,” the senior Senate Democratic aide said.

Durbin said the president’s outreach to GOP Senators was crucial.

“The president is meeting with a number of Republicans, talking to them on the phone. He has a number of people that he’s talking to that are encouraging. I hope he’s being persuasive. And if he is, then we’ll pass this,” he said.

But most Republicans aren’t budging given their public relations success in tagging the bill as pork-laden and not stimulative.

In fact, conservative Republicans from both chambers on Wednesday urged Obama to call a “time out” on the measure and refocus it on tax cuts and the housing crisis — something that Obama and Speaker Nancy Pelosi (D-Calif.) rejected.

“People are running scared in the Senate because this bill is stinking up the place,” Sen. Lindsey Graham (R-S.C.) said.

And Sen. Jim DeMint (R-S.C.) took issue with Obama’s contention that some of the tax cuts that Republicans are pushing helped get the country into the mess that it is now in. “He’s trying to blame our problems on a free people,” he said, arguing that it was bad government policies, not tax cuts, that sent the country into a recession.

Pelosi said that while she remains proud of the House-passed package, she’s willing to incorporate some Republican ideas into the final product. Still, the Speaker made clear the Democrats would only go so far.

“I reject and House Democrats have rejected the same warmed-over stew of bad, failed economic policies of the Bush administration that got us where we are today,” she said.

Steven T. Dennis contributed to this report.