The mechanism could trigger another $500 billion in across-the-board cuts by the U.S. Department of Defense over the next decade instead of targeted cuts of about $350 million if Congress doesn't pass a separate spending package.
"If that happened … it would result in a further round of 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," Defense Secretary Leon Panetta said this week.
Chairman of the Joint Chiefs of Staff U.S. Navy Adm. Mike Mullen, was of like mind, saying: "The Defense Department may represent 50 percent of the discretionary budget in this country but there is nothing discretionary about the things we do every day for our fellow citizens … the U.S. military remains the linchpin of defending our national interests."
"Debilitating and capricious" cuts threaten U.S. capability to meet threats, he said.
The United States spends about 5 percent of the nation's gross domestic product on defense when overseas operations are factored in. That's the largest of amount in the world.
A recent report by the Center for Strategic and International Studies, a Washington think tank, stated that U.S. spending accounted for about 46.5 percent of global military spending in 2009.
China, a potential adversary that is rapidly modernizing its military and that doesn't have overseas operations, accounts for about 6.6 percent of spending.
The rock-and-a-hard place the United States finds itself in on military spending ironically comes after former Secretary of Defense Robert Gates strongly chastised America's NATO allies for failing to adequately fund their militaries or even meet the NATO requirement of a minimum of about 2 percent of GDP.
Speaking to NATO members in June, he said the alliance had turned into a "two-tiered" organization. There were those willing and able to bear the price of alliance commitments and those who won't share the risks and costs.
The Pentagon since April has been looking at spending cuts under urging from U.S. President Barak Obama to trim $380 billion-$400 billion over the next decade, so the current plan is in line with that. But it's the doomsday mechanism of across-the-board cuts that has leaders worried.
"Make no mistake about it," Panetta said. "We will face some tough challenges here as we try to meet those numbers. But those numbers are within the ballpark that we were discussing with both the president and (Office of Management and Budget)."
Recommendations are due later this year. One big ticket program under scrutiny is the costly F-35 Joint Strike Fighter.
How the Pentagon handles the biggest portion of the defense budget -- personnel costs and benefits, such as healthcare for dependents and retirees, remains to be seen.
"We have to protect our core national security interests, we've got to be able to provide the best military in the world and we cannot break faith with the troops and their families," Panetta said.