It then lays out targets and enforcement mechanisms for compelling future reductions, including between $85 billion and $202 billion in Medicare and other health spending, $80 billion from defense, $70 billion from education and labor programs and $11 billion from agriculture programs, according to a summary.

It calls for a broad tax overhaul that would raise $1 trillion by limiting breaks for health, charitable giving, homeownership and retirement, while lowering individual and corporate tax rates. It would scrap the Alternative Minimum Tax, a system designed to prevent higher-earners from avoiding taxes.

About 50 senators, roughly evenly divided between the two parties, attended a closed-door briefing on the plan, a sign of potentially widespread support for the type of "grand bargain" to reduce the debt that Obama is urging.

Alexander Endorsement

One member of the Republican leadership, third-ranking Senator Lamar Alexander of Tennessee, endorsed the proposal.

Obama called it a "balanced" plan that may offer potential for a bipartisan consensus.

Also praising it were former White House budget director Alice Rivlin, who served under Democratic President Bill Clinton, and former Senator Pete Domenici, a New Mexico Republican who headed the Budget Committee.

The Gang of Six proposal "recognizes that all parts of the budget must contribute to any long-term solution, including defense spending, tax expenditures and entitlements," Rivlin and Domenici said in a statement. Saying they hoped the plan "leads to agreement by the president and both houses of Congress," they called on "members of both parties to put the good of the country ahead of ideology and return our nation to a fiscally responsible path."

Republicans Cautioned

The pair are co-leaders of the Washington-based Bipartisan Policy Center's Debt Reduction Task Force, which has been cautioning Republicans about the potential hazards of breaching the U.S. debt ceiling.

Even as the Gang of Six's plan was greeted positively, Senate leaders cast doubt on whether it would provide the quick solution needed in time to raise the debt limit.

"There are a lot of practical, procedural difficulties" to advancing the plan during the next 13 days, said Senator Max Baucus of Montana, the Democratic chairman of the tax-writing Finance Committee. "The real question is: What can we accomplished prior to Aug. 2."