U.N. Secretary General Antonio Guterres is considering attending the annual commemoration of the atomic bombing of Nagasaki, according to diplomatic sources.

It would be the first time for a U.N. secretary general to attend the Aug. 9 anniversary. Guterres' predecessor Ban Ki Moon became the first U.N. chief to attend the event marking the Hiroshima atomic bombing in 2010.

The annual commemorations in the two cities are attended by Japan's prime minister and other leading politicians.

Nagasaki, in southwest Japan, was the second city to be targeted in 1945, only three days after Hiroshima in western Japan. The double atomic bombings took place late in World War II and heralded the start of the nuclear age.

Alongside his Hiroshima visit, Ban traveled to Nagasaki in 2010, laying a wreath at the memorial site before the actual ceremony.

"We see his proactive commitment to supporting the abolishment of nuclear weapons," said Koichi Kawano, chairman of the A-bomb victims liaison council at the prefecture's peace movement center.

Kawano said he hopes Guterres will encourage countries across the globe to work toward early entering into force of the U.N. treaty banning nuclear weapons adopted last year.

Guterres' possible visit to attend the 73rd anniversary of the bombing comes on the heels of his release last month in Geneva of his disarmament agenda, in which he said scrapping nuclear, chemical and biological weapons could "save humanity."

He warned that some 15,000 nuclear weapons remain stockpiled with hundreds of them that could be launched at a moment's notice.

"The existential threat that nuclear weapons pose to humanity must motivate us to accomplish new and decisive action leading to their total elimination," he said in the foreword of the document, called "Securing Our Common Future."

"We owe this to the Hibakusha -- the survivors of nuclear war -- and to our planet," he said, using the Japanese name for the victims of the nuclear bombs.

If realized, the visit would also come a little over a year after the Treaty on the Prohibition of Nuclear Weapons was adopted on July 7, 2017.

The nuclear ban treaty was passed with support from 122 U.N. members, but without backing from any of the major nuclear powers that constitute the five permanent members of the U.N. Security Council -- Britain, China, France, Russia and the United States.