More than 60 senators from both parties are calling on President Obama to lead them in developing a comprehensive plan to rein in record budget deficits, a powerful sign of bipartisan willingness to abandon long-held positions on entitlement spending and taxes.

In a letter sent Friday to the White House, the 64 senators urge Obama “to support a broad approach to solving our current budget problems” along the lines of recommendations issued last year by a presidentially appointed commission. That plan calls for sharp cuts in government spending, elimination or reduction of dozens of popular tax breaks and an overhaul of Social Security that would include raising the retirement age to 69 for today’s toddlers.

“While we may not agree with every aspect of the Commission’s recommendations, we believe that its work represents an important foundation to achieve meaningful progress on our debt,” the senators wrote. “By approaching these negotiations comprehensively, with a strong signal of support from you, we believe that we can achieve consensus on these important fiscal issues.”

The letter was drafted by Sens. Michael Bennet (D-Colo.) and Mike Johanns (R-Neb.), who said in a conference call Friday with reporters that it took them only a couple of days to convince a super-majority of their colleagues to sign the letter — 32 Republicans and 32 Democrats.

Neither Senate Majority Leader Harry Reid (D-Nev.) nor Minority Leader Mitch McConnell (R-Ky.) is among the signatories. But the list is fairly evenly split between Democrats and Republicans, they said, and includes members of both parties’ leadership, including Republican conference chairman Lamar Alexander (Tenn.) and Richard J. Durbin (D-Ill.) the No. 2 Democrat in the Senate.

“There’s no question entitlement reforms and tackling tax reform is going to be tough,” Johanns said. “We acknowledge it’s one thing to get 60 senators on a letter; it will be even tougher to get 60 senators on a [deficit-reduction] package.

“But we won’t have any chance unless the president joins us in this effort,” he said. “We feel very very strongly that a crisis looms and that we all have to engage.”

The White House issued a statement Friday agreeing with the letter’s goals, but without promising any specific action. Vice President Biden is already involved in congressional talks over short-term funding levels.

“The president agrees that any serious discussion of how to tackle our long-term fiscal situation needs to include entitlements and tax reform, which is why he committed to take on both in his State of the Union Address,” said White House spokeswoman Amy Brundage, noting that Obama included several such provisions in his most recent budget blueprint, including a five-year freeze on domestic spending and a plan to limit tax deductions for high earners.

“We believe it’s a positive development anytime Democrats and Republicans come together to work on one of our nation’s toughest challenges, and we will continue to work with members of Congress from both sides of the aisle to rein in our deficit, grow our economy, and win the future.”

Obama has declined to endorse the recommendations of his commission, which would reduce deficit spending by more than $4 trillion by the end of the decade. Savings of that magnitude would stabilize the national debt, which has been growing dramatically since the onset of the Great Recession in 2007, and put the nation in a position to begin paying it down.

While Obama has been slow to embrace the commission’s work, it has been kept alive in the Senate, where six members of both parties have been holding increasingly frequent meetings in hopes of coming up with a strategy for advancing the proposal. Friday’s letter demonstrates that the so-called Gang of Six talks enjoy broad bipartisan support, despite a steady barrage of partisan sniping over short-term measures to keep the government operational through the end of this year.

The effort has also survived a campaign by Senate Democratic leaders to take Social Security off the table. Reid and Sen. Charles Schumer (D-N.Y.), the third-ranking Senate Democrat, have repeatedly insisted that Democrats will not endorse any changes to the program, which provides income support to nearly 55 million retirees. Elderly voters abandoned Democrats in droves last fall after a campaign in which Republicans accused them of cutting Medicare, the government health insurance plan for retirees, as part of Obama's overhaul of the health care system.

Advocates of a balanced budget called Friday's letter an encouraging sign that momentum is building for serious budget reforms, despite the potential political risk to officeholders.

“This letter is another sign — following the work of the Fiscal Commission, and the ongoing negotiations with the Gang of Six — that members of the Senate appear ready to tackle the serious fiscal challenges facing the country,” said Maya MacGuineas, president of the bipartisan Committee for a Responsible Federal Budget, which has encouraged the Gang of Six talks. “No one would have predicted this a year ago, and now look at how many people are signing up to be a part of the solution.”