WASHINGTON — Defense Secretary Chuck Hagel put the Pentagon and Congress on notice Wednesday that he is considering fundamental changes to the size of the military's management and command structures, requiring sweeping and dramatic spending cuts that are likely to hit programs favored by lawmakers.

Hagel said in a speech to the National Defense University at Fort McNair that escalating spending to maintain benefits, existing military structures and replacements for aging weapons programs are devouring funding needed for critical operations, training and equipment.

The Pentagon, he said, must reevaluate the size of its management and military command structures, which continue to grow even as the overall force numbers decline.

"I am concerned that despite pruning many major procurement programs over the past four years, the military's modernization strategy still depends on systems that are vastly more expensive and technologically risky than what were promised or budgeted for," Hagel said.