The nominee to become the top US military officer warned on Tuesday it would be “extraordinarily difficult and very high risk” to cut $800 billion from defense spending as part of efforts to reduce the nation's $14.3 trillion debt.

Army General Martin Dempsey appeared to push back hard in his Senate nomination hearing against proposals gaining momentum in Congress to at least double President Barack Obama's slated defense cuts of $400 billion over the next dozen years.

“National security didn't cause the debt crisis nor will it solve it,” Dempsey, Obama's choice to become chairman of the Joint Chiefs of Staff, told the Senate Armed Services Committee in a written comment released in conjunction with the hearing.

The hearing on Dempsey's nomination coincided with a deadlock in Washington on finding a way to reduce the $1.4 trillion annual US budget deficit and $14.3 trillion debt ahead of an Aug. 2 deadline for raising the debt ceiling.

Obama earlier this year asked the Pentagon to find $400 billion in cuts to national security spending over the next 12 years. The Pentagon is reviewing how best to achieve that goal and is expected to present options to the president.

But lawmakers grappling with the debt issue have proposed even deeper cuts of $800 billion or even $1 trillion over the coming decade.

Asked about the proposals during his hearing, Dempsey said, “Based on the difficulty of achieving the $400 billion cut, I believe $800 billion would be extraordinarily difficult and very high risk.”

No Hollow Force

Top generals at a hearing in the House of Representatives echoed Dempsey's concerns about deep budget cuts. General Joseph Dunford, assistant commandant of the Marine Corps, said his service would have “challenges” in implementing its share of a $400 billion cut.

“I think if they were to exceed $400 billion we would start to have to make some fundamental changes in the capability of the Marine Corps,” Dunford said. That would mean a smaller force and a reassessment of its strategic mission.

General Philip Breedlove, vice chief of staff of the Air Force, said cuts of $400 billion would cause “quite some concern” about funds to replace its aging fleet. Strategic bombers are an average 34 years old, refueling tankers 47 years old and airlift planes 19.

“We have decided we will not go hollow” by keeping a large infrastructure the Air Force cannot afford to staff or maintain, Breedlove said, describing walking down a flight line in the 1970s and seeing planes without engines.

“We had maintained a certain amount of infrastructure in iron, but it was unflyable,” he said. “We can't afford to go there with the requirements of ... today. So a $400 billion cut would force us to constrict our force in order to maintain a ready and fit force to fight.”

“Beyond $400 billion,” he added, “we would have to go into a fundamental restructure of what our nation expects from our Air Force.”

US debt not biggest threat

At his Senate confirmation hearing, Dempsey distanced himself from comments about the debt by current chairman of the Joint Chiefs, Admiral Mike Mullen, who has called it “the single-biggest threat to our national security.”

“I wouldn't describe our economic condition as the single-biggest threat to national security,” he said in his written remarks. “There are a lot of clear and present threats to our security in the current operational environment.”

Dempsey acknowledged the US debt “is a grave concern” but said the country could not afford to “neglect the other instruments of national power” - both military and diplomatic - as it works to solve its fiscal problems.

Republican Senator John McCain, Obama's rival in the 2008 presidential election and a Vietnam war hero, criticized the rising pressure to cut military spending without first understanding the impact on strategy.

“Defense spending is not what is sinking this country into fiscal crisis, and if the Congress and the president act on that flawed assumption, they will create a situation that is truly unaffordable: the hollowing out of US military power and the loss of faith of our military members,” McCain said.