Gallery: Obama pays tribute at Hiroshima

Gallery: U.S. President Barack Obama, right, and Japanese Prime Minister Shinzo Abe take a closer look at the Atomic Bomb Dome after laying a wreath at the cenotaph for victims of the 1945 atomic bombing at Hiroshima Peace Memorial Park in Hiroshima, western Japan, Friday, May 27, 2016. Obama on Friday became the first sitting U.S. president to visit the site of the world's first atomic bomb attack, bringing global attention both to survivors and to his unfulfilled vision of a world without nuclear weapons. Obama touched down in Hiroshima after completing talks with world leaders at an international summit in Shima, Japan.

Gallery: U.S. President Barack Obama gives a speech next to Japanese Prime Minister Shinzo Abe at Hiroshima Peace Memorial Park in Hiroshima, western, Japan, Friday, May 27, 2016. Obama on Friday became the first sitting U.S. president to visit the site of the world's first atomic bomb attack, bringing global attention both to survivors and to his unfulfilled vision of a world without nuclear weapons. The Atomic Bomb Dome is seen in the background.

Gallery: President Barack Obama embraces Shigeaki Mori, a survivor of the U.S. atomic bombing of Hiroshima in 1945, after speaking during a wreath-laying ceremony at the Hiroshima Peace Memorial in Hiroshima, Japan, May 27, 2016. Obama's visit to Hiroshima was the first by a sitting U.S. president since the atomic bomb was dropped there during World War II.

Gallery: U.S. President Barack Obama, center, accompanied by Japanese Prime Minister Shinzo Abe, left, shakes hands and talks with Sunao Tsuboi, a survivor of the 1945 Atomic Bombing and chairman of the Hiroshima Prefectural Confederation of A-bomb Sufferers Organization (HPCASO), at Hiroshima Peace Memorial Park in Hiroshima, western Japan, Friday, May 27, 2016. Obama on Friday became the first sitting U.S. president to visit the site of the world's first atomic bomb attack, bringing global attention both to survivors and to his unfulfilled vision of a world without nuclear weapons. (AP Photo/Carolyn Kaster)

Gallery: A crowd waits along the road for the motorcade carrying President Barack Obama to Hiroshima Peace Memorial Park in Hiroshima, Japan, May 27, 2016. Obama's visit to Hiroshima was the first by a sitting U.S. president since the atomic bomb was dropped there during World War II.

Gallery: U.S. President Barack Obama gives a speech next to Japanese Prime Minister Shinzo Abe at Hiroshima Peace Memorial Park in Hiroshima, western, Japan, Friday, May 27, 2016. Obama on Friday became the first sitting U.S. president to visit the site of the world's first atomic bomb attack, bringing global attention both to survivors and to his unfulfilled vision of a world without nuclear weapons. The Atomic Bomb Dome is seen in the background.

Gallery: Japanese Prime Minister Shinzo Abe, right, delivers a speech next to U.S. President Barack Obama at Hiroshima Peace Memorial Park in Hiroshima, western Japan, Friday, May 27, 2016. Obama on Friday became the first sitting U.S. president to visit the site of the world's first atomic bomb attack, bringing global attention both to survivors and to his unfulfilled vision of a world without nuclear weapons. Atomic Bomb Dome is seen in the back ground.