(Bloomberg News) Republicans and President Barack Obama are squaring off again over federal spending, only this time the president wants to cut it and the Republicans want to increase it.

As a Senate committee begins work today on a bill authorizing next year's military budget, White House officials have threatened a veto of anything resembling a measure passed by the House last week that would add $4 billion to his request for the Pentagon.

With the war in Iraq over, the military involvement in Afghanistan winding down and federal spending squeezed by mounting debt, Obama has proposed reducing the defense budget by 4.9 percent from this year's level. Though the Joint Chiefs of Staff backed the plan, House Republicans challenged their advice. Howard "Buck" McKeon of California, the chairman of the Armed Services Committee, warned against letting the U.S. become a "paper tiger."

The fight has already spilled over into election-year politics. Republicans have usually depicted Democratic presidents as weak on defense, and Obama's challenger, Mitt Romney, called the president "reckless" for signing a law last year that could mean as much as $1 trillion less for the Pentagon over a decade if Congress fails to agree on a plan to reduce deficits and the debt.

Democrats say it is wrong to spend more on defense while cutting domestic programs. The House "puts the funding of an already bloated military budget ahead of any semblance of fiscal responsibility," said Representative Earl Blumenauer of Oregon before voting against the $554 billion bill.

Senate Democrats

Democrats, who control the Senate panel taking up the defense authorization measure, are likely to abide by Obama's spending limits, or even go "perhaps lower than the president's request," said Todd Harrison, a defense budget analyst at the Center for Strategic and Budgetary Assessments in Washington.

In fact, Obama's longer-term plan calls for a modest increase after the cut he is seeking for next year. In contrast to prior post-war periods, when the Pentagon was hit with major reductions -- 40 percent in the six years after Korea and 28 percent in the decade after Vietnam -- Obama's five-year plan calls for it to start getting a gradual 1.9 percent increase each year through 2017, without adjusting for inflation.

With or without the additional money passed by the House, U.S. military spending far outweighs that of any potential adversary.

Biggest Spender

U.S. spending accounted for 41 percent of global military expenditures in 2011, according to the Stockholm International Peace Research Institute. China accounted for 8.2 percent and Russia 4.1 percent, the Stockholm-based policy group said in an April report.

Historically, the argument over defense versus domestic spending has been settled with more money for each, said Larry Sabato, director of the University of Virginia's Center for Politics.

"This goes back a long way to the 1980s when Republicans controlled the Senate and got what they wanted on defense, and Democrats in the House got most of what they wanted on social spending," Sabato said in an interview. "That's the reason we started down this path toward giant national debt."

Getting to a middle ground may be tough this year with the U.S. facing more than $15 trillion in debt as well as a political atmosphere in which compromise "is seen as a dirty word," Sabato said.

Deficit, Debt

The developing slowdown in defense outlays has taken place in the midst of a contentious debate over the federal deficit, ballooning debt, spending and taxes.

In an effort to get a grand compromise last year, Congress passed the Budget Control Act of 2011, which required cuts of $487 billion from projected U.S. defense spending for the decade ending 2021. If a so-called supercommittee failed to get an agreement on how to reduce the deficit and debt, an additional $500 billion would have to come out of defense.

Those prospective cuts were seen as an incentive to get Republicans to compromise. The supercommittee couldn't agree, and the cuts are scheduled to take place starting in January.

Although McKeon, the House Armed Services chairman, supported the law, "he has come to regret that vote and is having buyer's remorse," said Tom Donnelly, a defense analyst at the American Enterprise Institute in Washington.

McKeon has said adding $4 billion to the Pentagon's 2013 budget request would keep ships the Pentagon wanted to retire and slow reductions in Marine Corps and Army forces. Those measures would ensure "the president's new defense strategy is not a paper tiger," McKeon said at a May 9 committee meeting.

Protecting 'Constituencies'

Defense Secretary Leon Panetta shot back at McKeon, saying the money added by the House is an attempt by Congress to "protect particular constituencies."

The Obama administration released a national security blueprint in January that the Pentagon has said would result in a smaller military over the next 10 years following the end of the wars in Iraq and Afghanistan.

The military services would decline to 1.32 million members on active duty by 2017, or 7.2 percent fewer members than the current level of 1.42 million, according to the Congressional Research Service.

The smaller force would still be capable of taking on terrorists as well as defeating aggression and projecting power in the face of opposition from countries such as China and Iran, according to the Pentagon.

Donnelly, the defense analyst, disagrees. "The U.S. military just needs more," he said in an interview. A smaller military may struggle to surge in a future conflict as it did in Iraq and Afghanistan, he said.

Election As Arbiter

This November's presidential election may be the arbiter of which view prevails, Donnelly said. A Romney victory may mean a stronger support for defense at the expense of social programs, he said.

"The age of austerity is not a geologic age," Donnelly said. "It's not the ice age. It's a choice" and if voters choose to keep social entitlement programs that take up 15 percent of the U.S. Gross Domestic Product, "then, yes, it's going to squeeze other stuff out" including military spending.

The House-passed defense authorization bill is H.R. 4310.