United Nations Secretary-General Antonio Guterres told Prime Minister Shinzo Abe in Tokyo on Wednesday that his visit to Japan this time is of momentous importance for him because he is set to become the first U.N. chief to attend the annual Aug. 9 remembrance ceremony for the victims of the 1945 atomic bombing of Nagasaki.

"Since I joined the U.N. many years ago, I have come to Japan at least once a year. But this visit has very special meaning," he told reporters during a joint news conference with Abe after the two met at the Prime Minister's Office.

"The voice of hibakusha is a fundamental message for peace. 'No more Nagasaki, never more Hiroshima, not any more hibakusha necessary' is also a message of the U.N.," said Guterres, a former Portuguese prime minister who served as U.N. high commissioner for refugees between 2005 and 2015.