"This (event) has become the symbol of mankind's enormous destructive power when it makes a distorted use of scientific and technical progress," the pope said.
"With war one always loses," he said. "The only way to win a war is never to wage it." (Video via the U.S. Army)
The comments continue the Vatican's campaign against nuclear weapons.
Francis called for global disarmament in December in a letter to the 2014 Vienna Conference on the Humanitarian Impact of Nuclear Weapons.
The Vatican urges stakeholders not to stop with initial progress: "Continued efforts and commitment on the part of all involved will be necessary in order for [the agreement] to bear fruit."
This video includes images from Getty Images.