The chairmen of President Obama's bipartisan deficit commission on Wednesday offered an aggressive plan to rebalance the federal budget by curbing increases in Social Security benefits, slashing spending at the Pentagon and other agencies, and wiping out more than $100 billion a year in popular tax breaks for individuals and businesses.

The blueprint drafted by former Clinton White House chief of staff Erskine Bowles and former senator Alan K. Simpson (R-Wyo.) would slice more than $3.8 trillion from deficits over the next decade, reversing a rapid run-up in the national debt that many fear has the country headed for crisis.

To meet that goal, Bowles and Simpson are proposing to slay a herd of sacred cows, including the tax deduction for mortgage interest claimed by many homeowners, the tax-free treatment of employer-provided health insurance and the practice of letting retirees claim Social Security benefits starting at age 62. The blueprint would raise the early retirement age to 64 and the standard retirement age to 69 for today's toddlers.

During a briefing for reporters, Bowles and Simpson stressed that the plan is theirs alone and acknowledged that it is unlikely to win support from a majority of the commission's 18 members, many of whom seemed startled Wednesday by its breadth and scope. Bowles called it "a starting point" as the panel attempts to forge an agreement by Dec. 1.

Obama, speaking Thursday at a news conference in Seoul where he is attending the G-20 conference, cautioned that "before anybody starts shooting down proposals, I think we need to listen, we need to gather up all the facts."

"If people are, in fact, concerned about spending, debt, deficits and the future of our country, then they're going to need to be armed with the information about the kinds of choices that are going to be involved, and we can't just engage in political rhetoric," the president said.

"I set up this commission precisely because I'm prepared to make some tough decisions," Obama said, adding that "I'm going to need Congress to work with me."

Balanced-budget advocates praised the seriousness of the effort, saying it has the potential to reframe the debate over taxes and spending that dominated this month's congressional elections, regardless of how many commission members ultimately support it.

"A White House commission has put out a credible plan to eliminate the deficit and debt. This has changed the rules of the game and, for the first time, things are serious," said Maya MacGuineas, president of the bipartisan Committee for a Responsible Federal Budget, who hailed the blueprint as "a breakthrough."

"After this," she said, "the debate simply cannot go back to silly games where people pretend that eliminating earmarks will solve the problem."

Still, the reaction was harsh in some quarters, particularly among liberals who have vowed to protect retirees from any reduction in benefits. House Speaker Nancy Pelosi (D-Calif.) called the plan "simply unacceptable."

Speaker-in-waiting John A. Boehner (R-Ohio) declined to comment, saying he would discuss the plan with his three representatives on the panel. But Republican anti-tax activist Grover Norquist was not happy and warned that Republicans who support the proposal would be breaking their pledge not to raise taxes.