The United States on Friday for the first time attended a ceremony commemorating its atomic bombing of Hiroshima, 65 years after the Japanese city's obliteration rang in the nuclear age. Representatives from more than 70 nations joined tens of thousands at the emotional event, held under an azure sky as clear as that on the morning of August 6, 1945 when Hiroshima was transformed into a terrifying inferno. The United States' World War II allies Britain and France, both declared nuclear powers, also sent their first diplomats to the ceremony in the western Japanese city in a sign of support for the goal of nuclear disarmament. The mournful toll of a temple bell marked the start of a one-minute silence at 8:15 am, when the US B-29 bomber Enola Gay had dropped a history-making device that instantly killed tens of thousands in Hiroshima. 'The human race must not repeat the horror and misery caused by atomic bombs,' Japanese Prime Minister Naoto Kan said in a speech after 1,000 white doves were released in a symbolic gesture for peace. 'Japan, as the only nation to have been attacked by war-time atomic bombs, has a moral responsibility to lead the efforts toward realisation of a world without nuclear weapons,' he said. 'Little Boy', the four-tonne uranium bomb detonated over Hiroshima, caused a blinding flash and a fireball hot enough to melt sand into glass and vaporise every human within a one mile (1.6 kilometre) radius. An estimated 140,000 people died instantly in Hiroshima or succumbed to burns and radiation sickness soon after the blast, and over 70,000 perished as a result of another US atomic attack on the port of Nagasaki three days later. Japan, a wartime ally of Nazi Germany, surrendered on August 15, ending the war in the Pacific after years of ferocious combat with US Marines on islands strung across the ocean. The United States has never acceded to demands in Japan for an apology for the loss of innocent lives in the atomic bombings, which many Western historians believe were necessary to bring a quick end to the war and avoid a land invasion that could have been even more costly. US ambassador John Roos, whose attendance reflected a shift in policy under Nobel Peace Prize-winning President Barack Obama, in a statement urged collaboration 'to realise a world without nuclear weapons'. Secretary of State Hillary Clinton said Thursday that Obama 'thought it appropriate' to recognize the anniversary as he vies to rid the world of nuclear arms. Some saw Roos's attendance as an indication that Obama would visit Hiroshima during a trip to Japan later this year, as the sides seek to improve ties following controversy over an agreement to relocate a US airbase in Okinawa. Kan voiced hopes for an Obama visit. 'It will be very meaningful if his visit to Hiroshima and Nagasaki comes true,' he said, according to Jiji Press. Hanako Nogami, 92, braved the hot weather to attend the ceremony to pray for the soul of her brother, who was in Hiroshima at the time of the bombing, and whose remains were never found. 'I looked for him for days after the bombing, but he was nowhere to be found,' she told selfnews. United Nations Secretary General Ban Ki-moon also attended, becoming the first UN chief to take part in the annual event at the Hiroshima Peace Memorial. Ban, who visited Nagasaki Thursday, reiterated his call for the abolition of nuclear weapons and said he would convene a conference on disarmament in New York in September. '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,' Ban said. Two decades after the Cold War ended, the United States and Russia still have more than 22,000 nuclear warheads between them. France, Britain, China, India, Pakistan and Israel have a combined total of about 1,000, says the International Commission on Nuclear Non-proliferation and Disarmament. The global stockpile is equivalent to about 150,000 Hiroshima bombs. 