Ban Ki-moon is in Japan for ceremonies commemorating the 65th anniversary of the atomic bombing of Hiroshima and Nagasaki.
Mr. Ban will be the first U.N. secretary general ever to attend the Peace Memorial Ceremony, held every year on August 6 at the exact hour an atom bomb was dropped on Hiroshima. He will also be the world body's first leader to visit Nagasaki, where a bomb fell three days later.
Mr. Ban met Tuesday with Foreign Minister Katsuya Okada in Tokyo, where he said his visit was meant to send a message about the need to work for global nuclear disarmament.
He was expected to meet Wednesday with Prime Minister Naoto Kan before traveling to Hiroshima.
The two bombs killed more than 200,000 people during the final stages of World War II.
Some information for this report was provided by AFP.