The Pentagon got nearly everything it asked for during a decade of two wars shadowed by the Sept. 11 terror attacks and the rise of al-Qaida. No more.

Defense Secretary Leon Panetta and Joint Chiefs of Staff Chairman Adm. Mike Mullen acknowledged that reality Thursday, saying the military is resigned to budget cuts of around $350 billion over a decade to meet the public clamor for reducing the nation's debt. But they quickly warned that more than doubling those cuts along the lines of the "doomsday mechanism" spelled out in the new debt-limit law would undermine the military.

"If it happened — and, God willing, that would not be the case — but if it did happen, it would result in a further round of very dangerous cuts across the board, defense cuts that I believe would do real damage to our security, our troops and their families, and our military's ability to protect the nation," Panetta told reporters at his first Pentagon news conference.

Mullen, who has said repeatedly that the debt is the greatest national security threat, said any cut on that order "jeopardizes our ability to deal with the other very real and very serious threats we face around the world."

Reflecting the widespread demand for fiscal austerity, the compromise debt deal struck by President Barack Obama and congressional leaders this week will slice $350 billion from projected military spending over the next 10 years, and it leaves open the possibility of more than $500 billion in additional reductions.

Defense spending, which has nearly doubled in the last decade, is no longer untouchable in Washington.

Tea partyers and fierce fiscal conservatives in Congress are more willing to include Pentagon dollars in their mix of budget cuts despite opposition from veteran defense hawks. The death of Osama bin Laden, the diminished role of al-Qaida and the winding down of wars in Iraq and Afghanistan have prompted some lawmakers to question the need for such robust military spending.

Among the things that could be on the block: A troubled new jet fighter, expensive plans to modernize the nation's nuclear arsenal and perhaps some of the gold-plated benefits now guaranteed to military retirees.

"I think programs that can't meet schedule, that can't meet cost ... requirements are very much in jeopardy and will be very much under scrutiny," Mullen said.

The prospect of nearly $1 trillion in cuts unnerves military leaders, troubles lawmakers protective of the Pentagon and has touched off a scramble in the defense industry as contractors look to spare their multibillion-dollar weapons programs.

In sounding an alarm, Panetta is pressuring Democrats and Republicans to consider making concessions on their core priorities — entitlement programs such as Medicare and Social Security defended by Democrats, and increases in taxes resisted by Republicans — before taking a sharper knife to defense. The former Democratic congressman and budget chief in the Clinton administration delivered a clear message to leaders of both parties.

"You cannot deal with the size deficits that this country is confronting by simply cutting the discretionary side of the budget," said Panetta. "If you're going to deal with those size deficits, you've got to look at the mandatory side of the budget, which is two-thirds of the federal budget, and you also have to look at revenues as part of that answer."

Just back from a trip to Iraq and Afghanistan, Mullen faced repeated questions from troops worried that their pay and benefits would be cut.

"Our men and women downrange have enough to worry about just getting the job done," Mullen said Thursday. "They shouldn't also be concerned about whether or not they will be paid to do that job, or whether or not their families will continue to get the support they need during long absences."

Sitting side-by-side with Panetta at the Pentagon, Mullen pointed out that the military has a crowded must-do list: wars in Iraq and Afghanistan, support for the NATO-led operation in Libya, disaster relief missions in Haiti and Japan and defense of national interests.

Clearly reflecting the frustration building around the Pentagon and across the military, the defense leaders made it clear that while they will find the nearly $400 billion in initial savings required, that's where they draw the line. Military leaders think they are already carrying their fair share of the cost-cutting burden while still being asked to respond to terrorist threats, nuclear-armed rogue nations and other conflicts.

Defense budgets, not including the costs of the wars in Iraq and Afghanistan, have jumped since 9/11, from just over $370 billion in the late 1990s to around $550 billion today. In the political clamor to slash the deficit, Obama this past spring called for $400 billion in defense cuts over 12 years and former Defense Secretary Robert Gates launched a comprehensive review of the military's strategy and capabilities.

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

Setting the agenda now is the debt-limit deal to cut more than $2 trillion from federal spending over a decade.

In the initial phase, all security spending — money for defense, homeland security, veterans, foreign aid and intelligence — would be cut from the current level of $687 billion this year to $683 billion in next year's budget. Defense would take a share of that $4 billion reduction.

The next step is the unknown that Panetta fears: A 12-member, House-Senate committee must propose up to $1.5 trillion more in government-wide cuts over a decade and do so by Nov. 23. If the committee deadlocks or if Congress rejects its recommendations, the Obama administration would be required to impose automatic, across-the-board spending cuts of up to $1.2 trillion, with half coming from defense.

The budget proposals provide no specifics, but several programs are often mentioned as possible targets.

Ten years in, the F-35 Joint Strike Fighter, a multibillion-dollar aircraft, has been plagued by cost overruns and delays. The cost of buying more than 2,400 of the next-generation aircraft for the Air Force, Navy and Marine Corps has jumped from $233 billion to $385 billion. Recent estimates say the entire program could exceed $1 trillion over 50 years.

Another potential target is the Medium Extended Air Defense System (MEADS), a multinational missile defense program with Italy and Germany. The Pentagon said earlier this year it would not implement the program, though research will continue for another two years at a cost of more than $800 million. Among the other targets are the numbers of ships and submarines the Pentagon buys.

One of the most costly programs for the Defense Department is its health care coverage for some 10 million active duty personnel, retirees, reservists and their families. The cost has jumped from $19 billion in 2001 to $53 billion.

Obama proposed increasing the fees for working-age retirees in the decades-old health program, known as TRICARE, but has encountered resistance from lawmakers and various associations for military retirees.

Debt-limit negotiators looked at changes in the program for possible savings, and the special bipartisan committee is likely to consider the program in its calculations.

Mullen noted that while the Army and Marine Corp have grown over the past 10 years, those numbers will be reduced in the next several years. The Army already is on pace to drop from 570,000 to about 520,000, and the Marines will cut about 15,000 from their current total of about 202,000.