He added that this could result in freeze in pay hike, cut in troop numbers and new weapons programs.
"If sequester-level cuts persist, DOD would experience nearly USD 1 trillion in defence spending reductions over the next 10 years," said Hagel as he announced a series of administrative measures, to face the challenge of budgetary cuts in coming years.
"These measures include consolidations of regional combatant commands, defence agency mission cuts, and further IT consolidation" he said.
"The President's defence strategic guidance anchored this effort" he said adding that the goal was to find savings that best preserve the tenets of the president's strategy, such as strategic deterrence, homeland defence, and the re balance to the Asia Pacific.
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"With the end of the war in Iraq, the draw down in Afghanistan, and a changing requirement to conduct protracted large-scale counterinsurgency operations, it makes sense to take another look at the Army's force structure, which is currently planned to reach 490,000 in the active component and 555,000 in the reserves," he said.
Similarly, the Air Force could reduce tactical aircraft squadrons, potentially as many as five, and cut the size of the C-130 fleet with minimal risk," Hagel said.
In the months ahead, Hagel said he will work closely with Chairman Martin Dempsey, Chairman of the Joint Chiefs of Staff, to reach agreement on the proper size of our armed forces, taking into account real-world needs in a dangerous world.
"We would protect investments to counter anti-access and area-denial threats, such as the long-range strike family of systems, submarine cruise missile upgrades, and the Joint Strike Fighter, and we would continue to make cyber capabilities and special operations forces a high priority," said the Defence Secretary.
This strategic choice would result in a force that would be technologically dominant, but would be much smaller and able to go fewer places and do fewer things, especially if crisis occurred at the same time in different regions of the world, he said.