President Obama and his Democratic allies in Congress are poised to trample Republican opposition to his health care bill with a controversial legislative tactic known as reconciliation.

The fast-track process would protect Obama's ambitious plan to overhaul the U.S. health care system from a potential GOP filibuster and limit the Republicans' ability to get concessions. It also would give Democrats far more control over the specifics of the health care legislation.

Under typical Senate rules, 60 votes are needed to advance a bill, but reconciliation would enable Democrats to enact the health care plan with just a simple majority and only 20 hours of debate.

Democrats hold 56 seats in the Senate, and two independents typically vote with the party. Republicans have 41 seats, and there is one vacancy.

Republicans have complained furiously about the prospect of health care reform passing under fast-track rules. But they're not planning to go down without a fight.

A GOP Senate committee aide told FOXNews.com that Republican lawmakers are considering offering amendments to the legislation that would be unpalatable to Democrats.

Senate Republicans made a similar move with the D.C. Voting Rights Bill, which would have given the city its first seat in the House, by adding a controversial amendment that would repeal most of the District's local gun-control regulations. That bill now is waiting for a vote in the House.

For the health care bill, Republicans would try to add amendments that require employers to provide a certain number of dollars for every employee and limit the ability of uninsured Americans to choose health care providers, "specific changes that Democrats have said will not be included in any comprehensive health care plan," the aide said.

"I would assume this is the only option left," the aide told FOXNews.com.

But Democrats aren't stopping at health care. Obama's plan to cut private banks and other lending institutions out of the market for student loans would also move on a filibuster-free path.

Senate Majority Leader Harry Reid, D-Nev., said Friday that most House and Senate negotiators have resolved most of their differences over a congressional budget blueprint designed to advance Obama's agenda through Congress. The measure will set the rules on how Congress considers Obama's agenda for the rest of the year.

Lawmakers are rushing to agree on the budget framework in time to give Obama a victory within his first 100 days in office.

The negotiations have centered on the annual congressional budget resolution, which sets the parameters for the legislation that follows. Congressional votes next week would provide a symbolic victory for Obama's sweeping agenda to enact a universal health care system, invest in education and clean energy and cut the exploding budget deficit to manageable levels.

Obama marks his 100th day in office on Wednesday.

Hoping for a better chance at passing Obama's health care bill, Democrats have agreed to allow the president's signature $400 tax cut for most workers to expire after next year.

Obama's "Making Work Pay" tax cut of $400 for most workers and $800 for couples would expire at the end of 2010 as currently scheduled. The temporary tax cut was part of the economic stimulus plan enacted in February, and Obama is proposing to make it permanent.

The fast-track process could have a downside for Obama, since it's sure to anger Republicans whose support could help with business, insurers and other key interest groups.

Democrats, including Obama, have said repeatedly that they want the health care debate to be bipartisan and that the filibuster-proof terms would be used only if the GOP obstructs. But Republicans say the move has already poisoned the debate.

"Reconciliation is basically a nuclear weapon to use against the negotiators so what happens is nobody negotiates seriously because they can always go to reconciliation ... tilting the playing field unfairly," said Sen. Judd Gregg of New Hampshire, top Republican on the Budget Committee.

Sen. Max Baucus of Montana, one of the leading Democrats trying to write a health care bill, said Friday that going the fast-track route would only complicate matters, because Republican support is needed to pass legislation that would be broadly accepted.

"When you jam something down somebody's throat, it's not sustainable," Baucus told reporters. "And I want something that will last."

The Associated Press contributed to this report.