President Obama is under fire from Republicans for backtracking on proposed Social Security and other benefit cuts in his upcoming budget proposal.

The White House confirmed Thursday that the president’s forthcoming budget blueprint would no longer contain what had been a central component of his long-term debt-reduction strategy. In years past, Obama had offered to trim cost-of-living increases in Social Security and other benefit programs – known as chained CPI. Not anymore.

“This reaffirms what has become all too apparent: the president has no interest in doing anything, even modest, to address our looming debt crisis,” House Speaker John Boehner’s spokesman Brendan Buck said in a statement.

He added: “With three years left in office, it seems the president is already throwing in the towel.”

White House officials said Friday that the only reason they put these Social Security trims in last year's budget was as a carrot to Republicans to try and jump-start talks on a "grand bargain" budget deal. But they argue that Republicans never came to the table with a plan of their own and so Obama was not going to make that Social Security offer this time.

Liberal groups and lawmakers had been mobilizing against the proposed cuts, which reflect a different way for the government to calculate inflation.

On Feb. 14, 16 senators wrote a letter to President Obama asking that he not go forward with the trims.

“These are tough times for our country. With the middle class struggling and more people living in poverty than ever before, we urge you not to propose cuts in your budget to Social Security, Medicare and Medicaid benefits – cuts which would make life even more difficult for some of the most vulnerable people in America,” they wrote.

The letter also states “Social Security has not contributed one penny to the deficit.”

Asked about the forthcoming budget plan, White House spokesman Josh Earnest said Thursday that the general offer from Obama “remains on the table” if proposals like closing tax loopholes are also considered.

“The president was willing to step forward and put on the table a concrete proposal. Unfortunately Republicans refused to even consider the possibility of raising some revenue by closing some loopholes that benefit only the wealthy and well connected,” Earnest said.

Although liberals are likely to laud the move, it’s also a sign that Obama has been unable to strike a grand bargain with Republican leaders.

Officials said Thursday that those potential reductions in spending, included in last year's Obama budget, had been designed to initiate negotiations with Republicans over how to reduce future deficits and the nation's debt. But Republicans never accepted Obama's calls for higher tax revenue to go along with the cuts.

One official said the offer would remain on the table in the event of new budget talks but that it would not be part of the president's formal spending blueprint for fiscal 2015.

The new Obama proposal would also eliminate congressionally mandated automatic spending cuts that are scheduled to continue kicking in through 2015 by adding $56 billion to the budget, evenly divided between military and domestic spending. That increase would include money for what the White House calls an "Opportunity, Growth, and Security Initiative."

That additional spending would be paid for with a mix of other spending cuts and the closing of some tax loopholes, officials said. They did not describe the specific cuts or tax changes.

Officials said the White House will retain other spending reductions in benefit programs that it has proposed in the past, including a requirement that wealthier Medicare recipients pay more.

The Obama budget would build on the recently passed bipartisan congressional agreement that signaled an end to the brinkmanship that defined recent fiscal confrontations.

Even though the Obama proposal does not include that significant debt-reduction idea, the White House says that passage of a separate overhaul of immigration law, combined with more slowly growing health care costs, would eventually result in a national debt that is lower as a share of the total economy than projected in past administration budgets. It says deficits as a share of the economy will be below 2 percent after 2025.

The administration's budget is expected to be more bullish about the fiscal picture than a recent forecast by the non-partisan Congressional Budget Office. Economists at CBO projected earlier this month that deficits would fall to 2.6 percent of the economy in 2015 and then rise to about 4 percent between 2022 and 2024.

Fox News' Ed Henry and The Associated Press contributed to this report.