WASHINGTON (AP) — House Republicans' "fiscal cliff" counteroffer to President Barack Obama hints at billions of dollars in military cuts on top of the nearly $500 billion that the White House and Congress backed last year, and even the fiercest defense hawks acknowledge that the Pentagon faces another financial hit.

The proposal that House Speaker John Boehner, R-Ohio, and other Republican leaders sent to the White House this week calls for cuts of $300 billion in discretionary spending to achieve savings of $2.2 trillion over 10 years. The blueprint offered no specifics on the cuts, although the Pentagon and defense-related departments such as Homeland Security and State make up roughly half of the federal government's discretionary spending.

By any credible calculation, the military, which is still coming to grips with the half-trillion-dollar cut in last year's deficit-cutting law, is looking at an additional $10 billion to $15 billion cut in projected defense spending each year for the next decade. It's a prospect that Republicans recognize is the new reality, with wars in Iraq and Afghanistan ending and deficits demanding deep cuts.

"Not too devastating," said Sen. John McCain of Arizona, the top Republican on the Senate Armed Services Committee. That's especially true compared with the alternative that McCain dreads — the double hit of tax hikes and automatic spending cuts dubbed the fiscal cliff.

If Obama and Congress are unable to reach a deal this month, the Pentagon would face across-the-board cuts of some $55 billion after the first of the year and nearly $500 billion over a decade. Defense Secretary Leon Panetta and military leaders have warned that such a meat-ax approach to the budget would do considerable harm.

"My job is to stop sequestration," McCain said, using the budgetary term for the automatic cuts.

Pentagon spending still has its congressional protectors, especially with job-producing weapons, aircraft and ships built in nearly every corner of the country. In the past decade, the base defense budget has nearly doubled, from $297 billion in 2001 to more than $520 billion. The amount does not include the billions spent on the wars in Iraq and Afghanistan.

The cuts Obama and Congress are talking about would be to projected spending that envisioned Pentagon budgets rising to levels of more than $700 billion a year in a decade. Tea partyers and fiscal conservatives recently elected to Congress have shown a willingness to cut defense, traditionally considered almost untouchable.

"We understand that in getting to an agreement that drives down the debt ... that there are going to be cuts," said Rep. Austin Scott, R-Ga., president of the 2010 freshman class in the House. "Making cuts strategically makes sense. Doing it through sequestration does not make sense.

"I would argue that intelligence, especially with regard to cybersecurity, is probably an area where we need to spend more money," Scott added. "I'm worried more about China using viruses and technology against our country than I am about their aircraft carriers. At the same time, look at other areas of the military and say, 'When is the next time we really need that weapon system?'"

Said Sen. Lindsey Graham, R-S.C., of additional cuts, "Potentially, yes, but not a trillion."

Lawmakers who are realistic about defense cuts suddenly have some significant reinforcements.

A coalition of prominent Republicans and Democrats, including former defense, state and treasury secretaries as well as military and congressional leaders, made an urgent plea Tuesday to Obama and Congress to reach a deal on the nation's finances.

At a news conference a few blocks from the Capitol, the group called the national debt "the single greatest threat to our national security." The coalition also was running full-page ads in major newspapers on Wednesday calling on Washington leaders to consider every possible step to help fix the fiscal crisis, from raising tax rates to changes to Medicare and Social Security to cuts in defense.

"In our judgment, advances in technological capabilities and the changing nature of threats make it possible, if properly done, to spend less on a more intelligent, efficient and contemporary defense strategy that maintains our military superiority and national security," the group said.

Among the members of the coalition are retired Adm. Michael Mullen, the former chairman of the Joint Chiefs of Staff; former defense secretaries Robert Gates and Frank Carlucci; Paul Volcker, the former chairman of the Federal Reserve; and former secretaries of state James Baker, Henry Kissinger and George Shultz.

Former Sens. Sam Nunn and John Warner, who once led the Armed Services Committee, also are members of the coalition.

Any deal between Obama and Boehner that avoids the fiscal cliff and reduces the deficit will still face some resistance among rank-and-file lawmakers over defense cuts, especially in the House. The reductions will be particularly hard for GOP lawmakers who were counting on Mitt Romney to win the White House and try to reverse the cuts in defense.

Some lawmakers said the nearly $500 billion in cuts in the budget deal last year were hard enough.

"I felt that those cuts were plenty deep," said Sen. Susan Collins, R-Maine, a member of the Armed Services Committee. "They caused considerable reduction in the number of service members and raised some concerns whether we're going to be stretched too thin, and whether we're going to hollow out the services."

Rep. Allen West, R-Fla., a retired Army officer, said the budget law cuts are "quite sufficient" and any more reductions would have a serious impact on the military.

"How many more combat tours of duty do you want these young men and women to be doing, five or six tours of duty?" West said. "We're starting to break our military's back. The world is a more dangerous place. After every major combat engagement, we decimate our military and then we try to ramp up to play catch up in the next war."

The next solution, West said, would be for some members of Congress "to put on a helmet and fix a bayonet and they could go fight."