WASHINGTON - The Pentagon and its supporters are bracing for the likelihood of much deeper reductions in the US military's budget, as budget negotiators now eye defense cuts of $800 billion or more over the next decade.

With talks intensifying ahead of an August 2 deadline to raise the US debt limit, lawmakers hoping to shape an overall budget deal have advanced proposals that would cut defense spending by more than double the $400 billion President Barack Obama proposed just three months ago.

Some proposals call for as much as $1 trillion in cuts over the next decade.

Against that backdrop, Obama's nominee for Army chief of staff, General Raymond Odierno, cautioned lawmakers on Thursday against slashing defense spending too deeply.

Odierno told members of the Senate Armed Services Committee that the United States has a history of shrinking its military too quickly after conflicts, only to have to rebuild later.

"We must avoid our historical pattern of drawing down too fast and getting too small," said Odierno, former commander of US forces in Iraq. "As we make difficult resource decisions, we must be thoughtful in understanding the risk we incur to our nation's future security."

Committee members expressed anxiety over the coming cutbacks, but generally agreed there was no avoiding them.

"We're the Armed Services Committee, so I suppose we understandably feel a special protectiveness of the military budget," Senator Joseph Lieberman told Odierno and other nominees for key military posts. But he added, "Everybody has to give in this crisis."

"Our national debt has become a national security problem, and therefore we've got to work together to cut it down," he said. "But we've got to be really careful about the impact of these cuts on our military."

Republican Senator Tom Coburn unveiled a deficit reduction plan earlier this week that included $1 trillion in defense cuts, much of it through changes to the military's healthcare system, reducing the nuclear weapons force structure and canceling or delaying arms programs.

Another package of proposed cuts, by the so-called Gang of Six senators, came under fire from the chairman of the House Armed Services Committee, Buck McKeon. The California Republican warned that it included $886 billion in national security cuts and said he opposed it.

SEARCH FOR $400 BILLION IN CUTS

Obama earlier this year asked the Pentagon to find $400 billion in defense savings over the next dozen years.

Former Defense Secretary Robert Gates, who stepped down at the end of June, had already trimmed projected defense spending by $78 billion over five years and said the additional cuts would require real reductions in military capability.

Gates launched a review to develop options that would allow the president to decide where best to make reductions. That review is still under way.

General James Cartwright, vice chairman of the Joint Chiefs of Staff, told defense writers last week he was already evaluating the impact of budget cuts beyond $400 billion.

"The reality is you're most worried about a deeper cut. Is there another $400 billion behind the first $400 billion?" he said. "If that's the case ... you start to look at things like, do I want to hollow out the force, do I want to start to reduce the force size?"

He said in cutting short-term spending, the Pentagon has to look at things like reducing operating expenses and cutting readiness costs. Over a three- to six-year horizon, it can begin to change its structure, reduce forces or shift between reserve and active troops.

And over the long term - beyond six years - it can look at cutting infrastructure and entitlements, like closing bases or changing healthcare.

Defense Undersecretary Ashton Carter, the Pentagon's top arms buyer, told a Brookings Institution audience last week that more than big weapons systems are on the table.

Carter said that for every 30 cents the Pentagon spends on defense systems, it spends 70 cents to keep them functioning - a $100 billion annual maintenance budget. He said it was a part of the budget that received less scrutiny but was "deserving of examination."