August 6 marks the 65th anniversary of the atomic bomb dropped by the United States at the end of World War II on Hiroshima. Another was dropped a few days later on Nagasaki. The bombs devastated both cities and killed more than 200,000 people.

"Together, we are on a journey from ground zero to global zero -- a world free of weapons of mass destruction," Ban said. "That is the only sane path to a safer world. For as long as nuclear weapons exist, we will live under a nuclear shadow."

This is Ban's first visit to Hiroshima. He also made the first visit of a U.N. secretary-general to Nagasaki when he participated in a wreath-laying ceremony on August 5.

Ban called for his plan for nuclear nonproliferation and disarmament to be acted upon. "It includes recommendations on security, verification, transparency, conventional weapons and the legal framework for nuclear disarmament".

In Hiroshima, Ban noted recent success in the nonproliferation movement. "We see new leadership from the most powerful nations. We see new engagement in the U.N. Security Council. We see new energy from civil society," he said.

Ban said he will convene a conference on disarmament in New York in September. "We will push for negotiations towards nuclear disarmament. A comprehensive nuclear test bans treaty. A fissile material cut-off treaty," he said.

United States Ambassador John Roos also attended, marking the first time the United States has sent an envoy to the Hiroshima memorial ceremony.