Russia carried out its largest air strike on Ukraine's energy system since its invasion in February 2022, damaging power units at a dam and causing blackouts for more than a million people
Obama has said he will not apologize or address the debate on whether the Aug. 6, 1945, dropping of the bombs on Hiroshima and on Nagasaki three days later was justified, but will honor all those who lost their lives in World War Two.
He will be accompanied by Japanese Prime Minister Shinzo Abe on the visit.