Pentagon chief Jim Mattis said Monday he was "shocked" by the poor state of the military's readiness to fight due to years of legal budget caps.

"I retired from military service three months after sequestration took effect," Mattis told the House Armed Services Committee, referring to the budget limits.

"Four years later, I returned to the Department (of Defense) and I have been shocked by what I've seen about our readiness to fight," he added.

"No enemy in the field has done more to harm the readiness of our military than sequestration."