WASHINGTON (CNN) -- Negotiators are working on a stimulus bill that has dropped to about $789 billion, several senators involved in negotiations and other Democratic sources told CNN.

That is lower than the House's $819 billion version and the Senate's $838 billion bill.

Democratic Sen. Ben Nelson said the total could change as discussions continue, but he said the senators were getting closer to reaching a deal.

"I never really know how close we are until you get right to the end, so seems that we're getting closer at least," said the Nebraska senator, who helped craft the Senate version of the plan.

"I don't see anything that would constitute a deal breaker," Nelson said.

Nelson, Republican Sen. Susan Collins and other centrist senators spoke as they returned to Senate Majority Leader Harry Reid's office to continue talks with White House Chief of Staff Rahm Emanuel and Budget Director Peter Orszag.

Before the stimulus bill can be signed into law, the House and Senate must reconcile the differences between their bills and pass a final version of the package.

Collins and others said they're narrowing their differences and remain optimistic they can reach agreement Wednesday.

President Obama wants the bill on his desk by Presidents Day, which is next Monday.

Nelson said some of the funding for education that was cut in the Senate has been restored.

The Senate reduced the spending in its bill in order to win over Republican votes, but Democrats in the House balked at cuts in education funding.

The Senate also slashed nearly $20 billion in school construction.

Nelson said they are trying to add the money back, but change the focus from construction to modernization.

Nelson said negotiators are scaling back a Senate-passed tax credit for homebuyers and likely eliminating a tax deduction for car buyers.

Sen. Max Baucus, D-Montana, who heads up the Finance Committee, said earlier that negotiators have kept a one-year patch of the alternative minimum tax in the bill -- something House negotiators had argued should be handled outside of the stimulus package.

The tax was intended to target the wealthy, but now hits many middle-class families.

Democrats in the Senate must hold on to at least two Republican votes in order to get the 60 votes needed to pass the bill. Not a single Republican voted in support of the House version of the bill, but the House Democrats have a large enough majority that they were still able to pass it. iReport.com: Share your thoughts on the stimulus package

Three Republican senators voted in favor of the package: Collins, Sen. Olympia Snowe of Maine and Sen. Arlen Specter of Pennsylvania.

They supported the bill after a bipartisan group of lawmakers reached a compromise agreement that trimmed billions in spending from an earlier version.

All three have said they may not vote for the final version if House Democrats add more spending projects to the legislation. Specter is the only one of the three who is up for re-election in 2010.

Specter said Wednesday he's aware of the political danger he's putting himself in, but action is needed to pump up the ailing economy.

"I understand the peril, but I didn't run for the United States Senate to further my own political interests," he said on CNN's "American Morning."

"I think when you have a decision like the one that we're facing now, there's only one way to respond and that's to respond with action."

When asked about the possible political backlash from his vote supporting the bill, Specter said. "It's a good plan, not a perfect plan. But a good plan and I'll take my chances."

Democratic leaders are trying to execute a broad framework that Democratic sources told CNN was hatched in an unpublicized White House meeting early Monday with Obama, Reid and Pelosi.

More differences that need to be reconciled:

·  The Senate version of the bill makes changes to the president's signature middle-class tax cuts. Obama campaigned on tax breaks for those making $75,000 or less. The Senate version provides tax breaks for individuals making $70,000 or less, or for couples making $140,000 a year or less. That's different from the $150,000 in the House bill.

·  The Senate bill, unlike the House version, would make the first $2,400 in unemployment benefits tax-free. Both the Senate and House bills extend the time that jobless workers can collect benefits.