Republicans on Tuesday disparaged President Barack Obama's proposed $3.7 trillion budget for next year for taking a pass on tackling long-term deficits by not calling for structural changes in big-ticket entitlement programs for the elderly.

"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."

Obama told a news conference that the budget he sent Congress will help meet his goal of cutting the deficit in half by the end of his first term. He said he looked forward to negotiations with Republicans in coming months on how to fix Social Security and Medicare.

"This is not a matter of, `you go first, I go first,' " he said. "It's a matter of everybody having a serious conversation about where we want to go and then ultimately getting in that boat at the same time so it doesn't tip over."

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

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, which ends Sept. 30, 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."

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.

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