WASHINGTON – President Barack Obama on Tuesday vowed to tackle costly but fiercely guarded medical, retirement and jobless benefits, as he sought to rebuff criticism he is not willing to address tough spending issues.

Facing allegations that his 2012 budget does not tackle the main causes of the country's soaring deficits, Obama insisted the plan, presented Monday, puts the US on a path to pay for what it spends by the middle of the decade.

Urging Republicans to cooperate, Obama also sought to enlist his detractors in a broader reform effort, offering to examine unemployment, disability, old-age and health benefits that have long been sacrosanct in Democratic politics.

"To get where we need to go, we're going to have to do more, bring down health care costs further, including in programs like Medicare and Medicaid, the single biggest contributor to our long-term deficits," Obama told reporters.

Medicare provides health insurance for Americans over 65 years old, while Medicaid provides treatment for the poor. Along with Social Security -- which covers unemployment, disability and other benefits -- the programs will cost $20.4 trillion in the next ten years.

At the same time Obama backed reforming the corporate tax code, a move that could spell vastly larger tax bills for the Republicans' normally stalwart big business allies.

The administration has called for lowering minimum tax rates while closing loopholes that mean few large firms pay anything close to the current nominal rate.

Obama also raised the prospect of individual tax reform, an enticing if fraught prospect in the run up to a presidential election.

"I believe we should strengthen Social Security for future generations, and I think we can do that without slashing benefits or putting current retirees at risk, and I'm willing to work with everybody on Capitol Hill to simplify the individual tax code for all Americans.

"All of these steps are going to be difficult, and that's why all of them will require Democrats, Independents and Republicans to work together."

Obama pointed to previous examples of bipartisanship during the Clinton and Reagan eras and under his own administration as evidence that a deal could be reached.

But there was little evidence of common ground on Tuesday as members of both parties and the administration flooded the airwaves with their verdict of the budget, with comments almost exactly split along party lines.