Prime Minister Fumio Kishida and former U.S. President Barack Obama on Saturday called for a world without nuclear arms amid Russian threats to use them in the war in Ukraine and North Korea's rapid development of its weapons programs.Looking back to when he became the first sitting U.S. president to visit the western Japan city in May 2016, Obama said his trip then "strengthened my own resolve to reduce the threat of nuclear weapons worldwide, and it is this same commitment that brings you all here today."The world is facing the "biggest threat of nuclear weapon use since the Cold War," he said, referring to the Ukraine crisis and concerns that North Korea may carry out its seventh nuclear test and first since September 2017.The International Group of Eminent Persons for a World without Nuclear Weapons was set up under the initiative of Kishida, a lawmaker from a constituency in Hiroshima who has pressed his vision of a nuclear-free world since taking office in October last year.The eminent persons meeting involves 15 members and is led by Takashi Shiraishi, chancellor of the Prefectural University of Kumamoto in southwestern Japan and an expert in international politics."