Dunford, the chairman of the joint chiefs of staff, was responding to a question posed by Lindsey Graham while testifying before the Senate Armed Services Committee on the defense budget.
"Some have suggested that we intentionally target civilians in the war on terror and we go back to using waterboarding or maybe even more aggressive interrogation techniques," the South Carolina Republican said. "What effect if any would this have on the war fighter?"
Dunford responded, "Those kind of activities that you've described, they're inconsistent with the values of our nation and quite frankly I think it would have an adverse effect."
Republican presidential candidate Donald Trump had previously expressed support for aggressive interrogations and targeting families of terrorists. While Trump later said he would never instruct the military to break the law, he has since pledged
to "broaden" the laws to allow torture, including but not limited to waterboarding.
At a Saturday rally in West Palm Beach, Florida, Trump said, "As far as waterboarding is concerned, we have to stay within the law... But hey, who here thinks that ISIS -- who chops off heads, who drowns people in a cage -- who here thinks ISIS stays within the laws?"
He added, "We're going to stay within the laws. But you know what we're going to do? We're going to have those laws broadened because we're playing with two sets of rules: their rules and our rules."
Graham, an Air Force veteran, was also a Republican presidential candidate, but low poll numbers caused him to suspend his campaign in December. He has vocally opposed Trump's getting the nomination.
Graham is now supporting candidate Ted Cruz, a Texas senator, who has said that waterboarding was not technically torture and that while he would not support its "widespread" use, he thought it could be applied in limited scenarios.
Dunford concluded by saying that waterboarding, torture, and targeting of civilians would damage the morale of American service members.
"There's many adverse effects it would have, one would be on the morale of the force and frankly what you are suggesting are things that actually aren't legal for them to do anyway," Dunford said.
Graham responded "I don't think I've ever met a tougher guy than you and I think it would hurt your morale if you were ordered to kill innocents."