US President Barack Obama on Friday became the first sitting president to visit the site of the atomic bombing in Hiroshima, Japan, where he called on world nations to “escape the logic of fear” and reduce their nuclear arsenals.

Obama, who was in the country while attending a G7 summit, visited the Hiroshima Peace Memorial Park and Museum with Japanese Prime Minister Shinzo Abe.

There he said that the memory of the Hiroshima bombing, which on August 6, 1945 killed 140,000 people, “must never fade…it fuels our moral imagination and allows us to change.” He likewise met and embraced survivors of the bombing.

While expressing regret over the bombings of Hiroshima and Nagasaki, Obama stopped short of issuing an apology which would have proven controversial both in the US as well as in China and South Korea, where there is lingering resentment over Japanese atrocities committed in World War II. Some bombing survivors have said an apology is no longer necessary.

His call for nuclear disarmament comes even as the North Korean regime continues to develop nuclear weapons and threaten to target Tokyo in a nuclear strike, as well as its southern neighbor.

At the Hiroshima Peace Memorial Museum, Obama wrote in the guest book: “We have known the agony of war. Let us now find the courage, together, to spread peace, and pursue a world without nuclear weapons.”

He also laid a wreath at the cenotaph, an arched monument in the Hiroshima Peace Memorial Park inscribed in Japanese with the words: “Let all the souls here rest in peace; For we shall not repeat the evil.”

Obama became the first sitting president to visit Hiroshima, with Jimmy Carter being the only other president to have visited the site. He arrived at Hiroshima back in 1984, four years after he was voted out of office.

The White House has been working on planning Obama’s visit to Hiroshima for the past six years, and earlier this year US Secretary of State John Kerry visited to lay the groundwork.