WASHINGTON — President Barack Obama’s $3.7 trillion budget for 2012 was quickly dismissed Tuesday by House Republicans for taking a pass on tackling historically huge federal deficits.

Obama told a news conference, meanwhile, that the budget he sent Congress will help meet his goal of cutting the deficit in half by the end of his first term and said he hoped to find common ground with Republicans. He also defended his decision to avoid overhauls in entitlement programs like Social Security and Medicare, saying the two parties need to work together to find compromise.

"There’s going to be a lot of ups and downs in the coming months as we get to that solution," the president said. "I’m confident that we can get this done."

House Republicans, though, were eager to launch a weeklong debate on their own package of deep cuts in domestic spending for the current fiscal year.

White House budget director Jacob Lew kicked off the administration’s defense of its proposed 2012 budget on Capitol Hill with an appearance before the House Budget Committee. Rep. Mike Simpson spoke for most of the Republicans on the panel in saying he doesn’t view the proposal — which mostly ignores the recommendations of Obama’s fiscal commission — as a serious one.

"In our nation’s most pressing fiscal challenges, the president has abdicated his leadership role," said House Budget Committee Chairman Paul Ryan, R-Wis. "When his own commission put forward a set of fundamental entitlement and tax reforms … he ignored them."

Lew countered that the Obama plan is a "tough budget" filled with cuts to programs the president himself supports.

Eager to please their conservative tea party supporters, Republicans are championing $61 billion in cuts to hundreds of programs for the remaining seven months of this federal fiscal year under a bill the House planned to debate Tuesday. AmeriCorps and the Corporation for Public Broadcasting would be completely erased, while deep cuts would be carved from programs for feeding poor women and children, training people for jobs and cleaning the Great Lakes.

Reductions of that magnitude this late in a fiscal year would have a jarring impact on many programs. The GOP-run House planned to approve the measure Thursday.

The proposed reductions have "showdown" written all over them. Republicans included them in a must-pass bill financing the government, which otherwise runs out of money on March 4. The Democratic-controlled Senate and Obama himself are sure to turn them down.

"We have consistently said it’s not our intention to shut down this government," House Majority Leader Eric Cantor, R-Va., said Monday of one possibility should there be an impasse. "That’s political talk and we ought to get that off the table and we ought to go about the real business of trying to cut spending."

Lew downplayed the possibility of a government shutdown.

"If we all work together in a bipartisan way to look for the things we can agree on and take some of the things that we can’t agree on off to the side, we can accomplish a great deal," Lew said.

Obama unveiled his fiscal blueprint a day earlier, a plan that mixes tax increases on the wealthy and some businesses, a five-year freeze on most domestic programs, and boosts for elementary schools, clean energy and airport security. The outline is a first step in what is likely to be a bitter partisan fight as Congress translates it into a parade of tax and spending bills.

Despite its savings, Obama’s budget projects a record $1.65 trillion deficit this year, falling to $1.1 trillion next year and easing thereafter. Even so, it stands to generate a mammoth $7.2 trillion sea of red ink over the next 10 years, a number that would be even larger had the president not claimed over $1 trillion in 10-year savings by winding down the wars in Iraq and Afghanistan.

Glaringly missing from the president’s budget was a substantial reshaping of Social Security, Medicare and other massive, automatically paid benefit programs that bipartisan members of his deficit-reduction commission had recommended last year. That leaves the nation under a black fiscal cloud as its aging population, prolonged lifespans and ever costlier medical procedures leave the government with enormous I.O.U.’s.

Most Republicans have also shied away from calling for savings from so-called entitlement programs, but that’s not stopped them from criticizing Obama’s failure to do so. Rep. Paul Ryan, R-Wis., chairman of the House Budget Committee, has called for such reductions, but would not predict Monday whether they would be included in the 2012 spending plan his panel plans to write this spring.

"The president punted on the budget, he punted on the deficit," Ryan told reporters. "That’s not leadership, that’s an abdication of leadership."

Overall, Obama’s budget claims $1.1 trillion in deficit reduction from tax increases and spending cuts over the next decade while protecting some — but not all — programs that Democrats cherish.

By 2021, Obama projects that $844 billion out of the $5.7 trillion federal budget would go toward paying interest on the government’s debt. Such interest payments would exceed the size of the entire federal budget in 1983.

Federal budgets often burrow into the minutest details of the bureaucracy, and Obama’s was no exception.

The State Department said it expected to save $5.3 million over the next three years by painting the roofs of its embassies and other offices in a heat-reflecting, energy-saving white color. And the U.S. Agency for International Development projected hundreds of thousands in savings by reducing the font size in its documents to reduce paper usage.

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Associated Press writer Matthew Lee contributed to this report.