Once unthinkable in a time of two wars, Democrats and Republicans alike are insisting that the billions spent on the military can be significantly cut back over the next decade as the nation struggles to reduce its spiraling debt.

Senate Majority Leader Harry Reid's plan to slash spending and increase the government's borrowing authority would cap spending by the Pentagon and other government agencies at $1.2 trillion. Conservative Sen. Tom Coburn of Oklahoma has called for just over $1 trillion in defense cuts in his "Back in Black" plan, including fewer weapons, fighter jets and personnel. A bipartisan group of six senators envisions reductions of more than $800 billion in 10 years.

The proposals reflect a rare bipartisan consensus driven by a dire economic outlook. The numbers even outpace what a Democratic commander in chief called for earlier this year. In April, President Barack Obama instructed the Pentagon to find $400 billion in defense savings over 12 years and said no decisions on specifics would be made until the Pentagon had completed a review of options for achieving such reductions.

No matter which plan emerges in the latest debt showdown _ Reid's or the House GOP plan by Speaker John Boehner, R-Ohio _ both call for creation of a 12-person, House-Senate bipartisan committee to find trillions in deficit cuts. Defense spending will be a ripe target, especially since the money would come from cuts in projected increases. Defense budgets, not including the costs of the wars in Iraq and Afghanistan, consistently have gone up in recent years, from just over $370 billion in the late 1990s to around $550 billion today.

Military leaders and lawmakers on the congressional committees overseeing the Pentagon warn of creating a "hollow" fighting force.

Army Gen. Martin Dempsey, Obama's choice for chairman of the Joint Chiefs of Staff, told a Senate panel this week that cuts of $800 billion or more "would be extraordinarily difficult and very high risk." Leaders in the Marine Corps, Air Force, Army and Navy told a House panel that cuts of that magnitude would force them to restructure their respective services and cause problems meeting the demands of commanders in the field.

"I'm deeply concerned that hasty across-the-board cuts will dramatically affect our safety and security of the men and women serving," said Sen. Scott Brown, R-Mass.

Rep. J. Randy Forbes, R-Va., said he worries "about our state of readiness, not for mastheads on the horizon or columns of tanks rolling toward us, but for the looming defense budget cuts many in this Congress seem willing to inflict on our military."

Facing critical votes on debt-limit bills, Senate Armed Services Committee Chairman Carl Levin, D-Mich., said in an interview that he backed Reid's legislation "even though I think it is an aggressive number for defense."

Reid's bill would start with caps on spending on defense, intelligence and veterans at $606 billion in the fiscal year beginning Oct. 1 and $607 billion the following year. The caps would essentially pare back the increases in military spending, standard for an agency that deals with long-term contracts for multimillion-dollar weapons and programs. Separately, he counted some $1 trillion in savings from eventually winding down the wars in Iraq and Afghanistan.

The demands for defense cuts come as Republicans fiercely oppose increases in taxes and Democrats say hands-off on entitlement programs such as Social Security and Medicare. That leaves the billions for defense and the scores of other government programs, from education to transportation to agriculture, for reductions as the nation grapples with a $1.5 trillion deficit.

"If Republicans are taking revenue completely off the table, it's unavoidable that defense, which is 20 percent of the budget, is going to face some significant reductions to get our deficit under control," Rep. Adam Smith of Washington, the top Democrat on House Armed Services, said in an interview. "It has to be on the table in any event, but once you take revenue off the table, defense is in serious trouble. That concerns me, but our deficit concerns me as well."

Smith said many in Congress were "brutally in denial" about how to solve the fiscal problem.

Although the long-range proposals favor significant defense cuts, many Republicans and Democrats have been reluctant this year to vote for reductions. Earlier this month, the House overwhelmingly backed a $649 billion defense spending bill that boosted the Pentagon budget by $17 billion. The legislation included $119 billion for the two wars. During debate, the House easily turned back efforts by liberal Democrats and tea party Republicans to slash billions.

Still, tea party-backed Republicans have prevailed on occasion, most notably in February when they led the effort to eliminate funds for a second engine for the next-generation F-35 fighter plane.

John Isaacs, executive director of Council for a Livable World and Center for Arms Control and Non-Proliferation, said if "tea party Republicans were willing to cut defense spending, it would give more courage to Democrats" worried about the weak-on-national security label they've often faced since the Vietnam War."

At the Pentagon, Defense Secretary Leon Panetta, who served as director of the White House's Office of Management and Budget, is overseeing a review of the consequences of budget reductions of $400 billion and above. Panetta's predecessor, Robert Gates, initiated the review and it would include an assessment of what changes in defense strategy would be required as a result of such cuts and how they would affect military capabilities.

The review could be completed by the end of the summer.