Barack Obama on Friday paid tribute to the 140,000 people killed by the world’s first atomic bomb attack, becoming the first incumbent U.S. president to visit Hiroshima. He also sought to bring global attention to his unfulfilled vision of a world without nuclear weapons.

“Death fell from the sky and the world was changed,” Obama said, after laying a wreath, closing his eyes and briefly bowing his head before an arched monument in Hiroshima’s Peace Memorial Park that honors those killed on Aug. 6, 1945, when U.S. forces dropped the bomb that ushered in the nuclear age.

The bombing, Obama said, “demonstrated that mankind possessed the means to destroy itself.”

Obama did not apologize, instead offering, in a carefully choreographed display, a simple reflection on the horrors of war and his hope the horror of Hiroshima could spark a “moral awakening.”

Atomic bomb survivors have said an apology from Obama would be welcome but for many, the priority is ridding the world of nuclear arms, a goal that seems as elusive as ever.

Not all agree. “I want Obama to say ‘I’m sorry’. If he does, maybe my suffering will ease,” said Eiji Hattori, 73, a toddler at the time of the bombing who now has three types of cancer.

“If Obama apologized, I could die and meet my parents in heaven in peace,” he said at the peace park, from which ordinary citizens were later ejected amid tight security ahead of Obama’s arrival.

Earlier, protesters outside the peace park could be heard demanding an apology.

As he and Japanese Prime Minister Shinzo Abe stood near an iconic bombed-out domed building, Obama acknowledged the devastating toll of war and urged the world to do better.

“We stand here in the middle of this city and force ourselves to imagine the moment the bomb fell … we listen to a silent cry,” Obama said.

A second atomic bomb, dropped on Nagasaki three days later Hiroshima, killed 70,000 more.

Obama also sought to look forward to the day when there was less danger of nuclear war. He received a Nobel Peace Prize early on his presidency for his anti-nuclear agenda but has since seen uneven progress.

“We must have the courage to escape the logic of fear and pursue a world without them,” Obama said of nuclear weapons.