Gates spoke Tuesday to the conservative American Enterprise Institute, The Washington Times reported.
"I am determined that we not repeat the mistakes of the past, where budget targets were met mostly by taking a percentage off the top," Gates said. "That kind of salami-slicing approach preserves overhead and maintains force structure on paper, but results in a hollowing out of the force from a lack of proper training, maintenance and equipment -- and manpower."
Gates said U.S. defense spending is not going to return to Cold War levels.
The secretary has made his own budget-cutting moves and has tried to shift the focus of the military to counterinsurgency. He has eliminated some weapons programs and plans to reduce the number of commands.