Britain and France also made their first official appearance at the memorial, as well as UN Secretary General Ban Ki-moon. Altogether, 74 nations were represented.
China, which sent a low-ranking official in 2008, did not participate. Officials said it did not give a reason.
Hiroshima was careful to ensure that the memorial emphasized a look-forward approach, focusing not on whether the bombing was justified, a point which many Japanese dispute, but on averting a future nuclear attack.
Roos said the memorial was a chance to show resolve toward nuclear disarmament.
“For the sake of future generations, we must continue to work together to realize a world without nuclear weapons,’’ he said in a statement.
Ban, who presented flowers at the Eternal Flame in Hiroshima’s Peace Memorial Park, said this year’s memorial would send a strong signal to the world that nuclear weapons must be destroyed.
“Life is short, but memory is long,’’ Ban said. “For many of you, that day endures . . . as vivid as the white light that seared the sky, as dark as the black rains that followed.’’
Washington’s decision to attend the anniversary has been welcomed by Japan’s government, but has generated complex feelings among some Japanese who see the bombing as unjustified and want the United States to apologize.
“Americans think that the bombing was reasonable because it speeded up the end of the war. They try to see it in a positive way,’’ Naomi Sawa, a 69-year-old former teacher, said after paying her respects to the dead. “But we were devastated.’’
About 140,000 people were killed or died within months when the American B-29 Enola Gay bombed Hiroshima on Aug. 6, 1945. Three days later, about 80,000 people died after the United States attacked Nagasaki.
The United States decided to drop the bombs on Hiroshima and Nagasaki because it believed that would speed up Japan’s surrender and avoid the tough battles expected to take Japan’s mainland. Fears of bloody battles were heightened by Japan’s intense defenses of outlying islands.
Concerns that attending the ceremony — an emotional event beginning with the offering of water to the dead and a moment of silence to soothe their souls — would reopen old wounds had kept the United States away.
Secretary of State Hillary Rodham Clinton told reporters in Washington yesterday that Obama believed “it would be appropriate to recognize this anniversary’’ by sending Roos.
The State Department deemed the time was right to do so, and it was a chance to push Obama’s goal of nuclear disarmament.
Hiroshima’s mayor praised that position.
“We are encouraged that our voice is being heard,’’ Tadatoshi Akiba said in a speech at the ceremony. “It is the wish of the survivors of the bombing that the voices of peace will be heard.’’
