WASHINGTON, June 10 (Xinhua) -- U.S. Defense Secretary Robert Gates noted on Tuesday the need for the Air Force to "restore excellence" in their nuclear mission, one day after he overhauled the force's leadership.

　　"Our policy is clear," he told about 500 airmen at the Scott Air Force Base in Illinois. "We will ensure the complete physical control of nuclear weapons, and we will properly handle their associated components at all times."

　　"It is a tremendous responsibility -- one we must not and will never take lightly," he added.

　　Gates announced on Monday his nominees for the Air Force's new chief of staff and secretary after the two predecessors both resigned last week over errors in the handling of nuclear weapons and parts.

　　In announcing the resignations, Gates said that systemic problems with the Air Force had been revealed from the two incidents -- the shipment of nuclear missile fuses to Taiwan and the cross-country flight by an Air Force bomber wrongly armed with nuclear weapons.

　　Gates told the airmen on Tuesday that the only reason he asked for the resignations was because of the degradation and systemic weakness in the Air Force's nuclear weapons program.

　　He also urged the whole U.S. military, not only the Air Force, to take in criticism from the outside its ranks.

　　"However, I have noticed that none of the services easily accept honest criticism from outside their branch, or scrutiny that exposes institutional shortcomings," he said. "This is something that must change across the military."