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(CNN) —  

A top commander in the U.S. military voiced concern Friday over a recent decision by the Pentagon to open up combat positions to women.

Marine Gen. John Kelly, the outgoing head of Southern Command, told reporters that in contemplating action on the battlefield, the key question is whether or not it makes the armed forces more lethal.

“If the answer to that is yes, then do it,” Kelly said. “If the answer to that is no, clearly don’t do it. If the answer to that is, it shouldn’t hurt, I would suggest that we shouldn’t do it, because it might hurt.”

Last month, Defense Secretary Ashton Carter announced that the military would open some 220,000 jobs to women – including infantry, armor, reconnaissance and some special operations units –that had been previously only open to men.

Kelly also said he anticipated pressure from “the agenda-driven people here in Washington” on future military leaders “to lower standards” in order to bolster the numbers of women in combat. The Pentagon has maintained that it would not lower standards to accept women, and several women have struggled in the most rigorous training courses and failed to advance.

Joint Chiefs Chairman Gen. Joseph Dunford, also a Marine, had advocated keeping some military roles restricted to men during the review when he served as the commandant of the Marine Corps. The Marines have been seen as the most reluctant branch to open up all combat jobs to women.

Kelly, whose own son was killed in combat in Afghanistan, was particularly candid in his assessment of future standards for women in the military as commanders work to integrate them into new roles.

Kelly, who is retiring from the Marine Corps, will be succeeded by Navy Vice Adm. Kurt Tidd later this month.