President Obama does not even formally unveil his proposed 2014 federal budget until next week, but the details of the blueprint being leaked early have both Republican leaders and Mr. Obama’s liberal base fuming.

Senior White House officials said Friday that the fiscal 2014 budget Mr. Obama has prepared cuts the deficit by $1.8 trillion over 10 years and changes the way annual Social Security benefits are calculated, while also calling for higher taxes.

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Because the president’s budget also would wipe out the $1.2 trillion in sequester cuts, Republicans argue that it would only produce $600 billion in net savings, a third of what the White House claims.

Mr. Obama’s spending blueprint will propose moving from the current inflation measure to the so-called “chained” consumer price index (CPI) to calculate Social Security benefits, to slow the program’s cost growth of by reducing payments over time to seniors and future retirees.

It also will call for higher-income beneficiaries to pay more for Medicare coverage, and for $600 billion in new revenue — most of which would come from capping the tax deductions that those in the higher tax brackets can claim.

Deluged with questions about the change to Social Security during Friday’s briefing with reporters, White House spokesman Jay Carney said the budget is not Mr. Obama’s “ideal plan” but instead a “good-faith effort” to strike a compromise deficit deal with Republicans.

While congressional Democratic leaders were largely silent on the White House budget early Friday, the proposed Social Security changes drew angry responses from some lawmakers and liberal groups who have warned that the new formula would make it harder for the nation’s retirees to keep up with the risings cost of health care.

Republicans also are rejecting the idea of new tax increases, arguing that they already agreed to tax increases as part of the “fiscal cliff” deal that passed Congress New Year’s Day. The budget focus now should be on spending cuts alone, they insist.

LIBERAL BLOWBACK

Robert Reich, former labor secretary under President Bill Clinton, said in a MoveOn.org press release this week that “Social Security is not driving the deficit, therefore it should not be part of reforms aimed at cutting the deficit.”

“The chained CPI, deceptively portrayed as a reasonable cost-of-living adjustment, is a cut to Social Security that would hurt seniors,” Mr. Reich said.

Sen. Bernie Sanders, Vermont independent, sent on an email Thursday that said the Democratic president was turning his back on a promise he made in 2008 not to cut Social Security.

“If Obama is serious about dealing with our deficit, he would not cut Social Security — which has not added one penny to the deficit,” Mr. Sanders said. “Instead, he would support legislation that ends the absurdity of one out of four profitable corporations paying nothing in federal income taxes. He would also help us close the offshore tax haven loopholes that enable large corporations and the wealthy to avoid paying $100 billion a year in federal taxes.”

One liberal group went so far as to show Mr. Obama the door out of the Democratic Party and vowed to recruit a primary opponent for any Democrat in Congress who votes for a plan that cuts Social Security.

“You can’t call yourself a Democrat and support Social Security benefit cuts,” said Stephanie Taylor, co-founder of the Progressive Change Campaign Committee. “… The president has no mandate to cut these benefits, and progressives will do everything possible to stop him.”

REPUBLICANS BALK AT TAXES

On the other side of the aisle, GOP House Speaker John Boehner called the changes to Social Security only “modest” and complained about reports that Mr. Obama only intends to offer them if Republicans are to increase taxes for the second time this year.

When the president visited the Capitol last month, Mr. Boehner said House Republicans stated a desire to find common ground and urged him not to make budget savings conditional on another round of tax increases.

“If reports are accurate, the president has not heeded that call,” Mr. Boehner said in a statement. “If the president believes these modest entitlement savings are needed to help shore up these programs, there’s no reason they should be held hostage for more tax hikes.”

“That’s no way to lead and move the country forward,” he concluded.

Meanwhile, groups devoted to safeguarding Social Security also complained that Mr. Obama appears to be using changes to the seniors’ entitlement program as a bargaining chip.

“Evidently the president either does not understand or does not care how critically important Social Security and Medicare are, not just to seniors but to middle-aged and younger workers for whom these programs are likely to be even more crucial,” Eric Kingson, a co-chair of the Strengthen Social Security Coalition.

During the election, Mr. Kingson points out, Mr. Obama pledged to protect the social safety net in this country — a promise he said Mr. Obama is now breaking.

“What he and other elites call ‘tweaks’ are deep cuts that will take away the bread and butter of seniors, people with disabilities, children who have lost parents, veterans who have served this nation and others,” he said. “He promised he would not slash benefits; he has broken his promise to the American people.”