Updated: 12:56 p.m.

The “gang of six” is back together, and they have a deal.

In fact, momentum surged Tuesday for the deficit reduction plan proposed by the gang of six Senators, with Sen. Tom Coburn throwing his support behind the plan and a broad group of Senators expected to announce their backing in the next 24 hours.

“I’m not on sabbatical,” the Oklahoma Republican said after a meeting with more than 50 Senators to discuss the plan. “I’m on board.”

Coburn previously walked away from the gang of six, citing differences over cuts to Medicare. But Tuesday, Coburn said it looks like about 60 Senators are likely to back the plan, which trims entitlements and other spending programs alongside more than $1 trillion in new revenue from shrinking tax breaks. Coburn’s comments came after the group briefed nearly 50 Senators on the plan Tuesday morning.

Coburn said he considers the deficit cuts in the plan a good start and significant enough to make a dent in the growing tide of debt.

The gang of six deal comes two weeks before the Treasury Department has said the U.S. will breach its debt limit. Lawmakers have been scrambling to come up with a deficit reduction deal to couple with any increase in the debt ceiling because some Republicans in the House and Senate have vowed to oppose upping the debt in the absence of such a plan.

Senate Budget Chairman Kent Conrad (D-N.D.) said Monday that the group’s plan includes $4.65 trillion in deficit cuts if lawmakers use the same baseline employed by the president’s fiscal commission. He said it cuts $3.6 trillion to $3.7 trillion relative to the latest Congressional Budget Office baseline.

Besides Conrad and Coburn, Senate Majority Whip Dick Durbin (D-Ill.) and Sens. Mark Warner (D-Va.), Mike Crapo (R-Idaho) and Saxby Chambliss (R-Ga.) are original members of the gang of six.

Chambliss said the group has basically agreed to the package, with the exception of a few small details. He said he hopes to brief House lawmakers as well in hopes of enlisting their support. Chambliss is a close friend of Speaker John Boehner (R-Ohio).

Chambliss said the package includes more than $1 trillion in new revenue, but he said that revenue would be scored by the CBO as a tax cut. It would shrink deductions, lower tax rates and permanently fix the alternative minimum tax so it does not affect the middle class.

Several Senators from both parties spoke positively of the plan to reporters after the meeting. Sen. Rob Portman (R-Ohio) called the plan and the positive reaction from Senators “encouraging.”

And Sen. Chris Coons (D-Del.) strongly backed the outline.

“This is the sort of big, balanced and bipartisan package that we need to move the country forward,” Coons said.

He added, “If Sen. Durbin and Dr. Coburn can both endorse it, this may be just the tough discipline fiscally and the balanced path forward that we need.”

Conrad said it’s not yet clear what role the plan would play in the debt ceiling debate. The group’s plan includes an upfront down payment reducing the deficit by $500 billion and requires nine Senate committees to produce legislation implementing the rest of the deal within six months, according to an outline obtained by Roll Call.

The top income tax rate would be lowered to no more than 29 percent under the plan; under existing law, the top rate is scheduled to reach 39.6 percent once the Bush tax cuts expire in 2013.

The plan also creates strict new spending caps that would require a 67-vote supermajority in the Senate to breach and shrink annual deficits to below 2 percent of the gross domestic product from about 10 percent this year.

The proposal also boosts spending on transportation but without raising the gas tax.

And the plan tackles Social Security, calling for reform that would ensure the program’s solvency for 75 years and plow any savings back into the program. It would be handled on a separate legislative track, but the overall package would not move forward without it.

Of note, the plan includes several enforcement mechanisms that would force spending cuts if committees fail to produce legislation. If any committee fails to produce their prescribed cuts, across the board cuts would be made in the programs under their jurisdiction, except programs for the poor. And any bipartisan group of 10 Senators — five from each party ­— would be able to get votes on an alternative package if committees fail to produce a result.

The proposal also subjects the plan and any amendments to a 60-vote threshold.

This week, the House and Senate are expected to vote on an austere Cut, Cap and Balance plan and possibly a constitutional amendment to balance the federal budget. Senate Minority Leader Mitch McConnell (R-Ky.) and Majority Leader Harry Reid (D-Nev.) also have continued working on a Plan B proposal that would give the president the authority to raise the debt limit but would allow Congress to vote on resolutions of disapproval. That plan would create a joint committee charged with drafting a larger deficit reduction package by the end of the year.