Terumi Tanaka, secretary-general of the Japan Confederation of A- and H-Bomb Sufferers Organizations (Nihon Hidankyo), will step down in light of his ill health and the need to pass leadership of the anti-nuclear movement to younger generations, sources said Saturday.

The successor to Tanaka, 85, will be chosen on the second day of the group's general meeting starting Tuesday in Tokyo, the sources said.

In May 2016, Tanaka participated in events in Hiroshima presided over by U.S. President Barack Obama, the first sitting American president to visit the A-bombed city.

Born in Manchukuo, a former Chinese puppet province of Japan during the war, Tanaka's family eventually returned to Nagasaki.

He was 13 when Nagasaki was devastated by the atomic bomb on Aug. 9, 1945, three days after the atomic bombing of Hiroshima and shortly before Japan surrendered to the Allies to end World War II. Although he was unhurt, Tanaka lost five relatives, including a grandfather and aunt.

Joining the campaign to raise public awareness of A-bomb survivors and related issues in the 1970s in Sendai, Tanaka took the helm of the group in 2000 and has led its anti-nuclear push ever since.

The confederation, known in Japanese as Nihon Hidankyo, was launched in 1956 with the goals of pressuring the government to provide compensation to A-bomb survivors and lobbying foreign governments to eliminate nuclear weapons.

In 2005, Tanaka contributed to holding a panel exhibition on atomic bombings for the first time at U.N. headquarters in New York, on the sidelines of an international conference to review the Nuclear Non-Proliferation Treaty.

He has continued to call for the abolishment of nuclear weapons in speeches at international forums such as an NPT review meeting by nongovernmental organizations in 2015.