The first US secretary of state to visit Hiroshima, Mr Kerry said US President Barack Obama also wanted to travel to the city in southern Japan but he did not know whether the leader’s complex schedule would allow him to do so when he visits the country for a Group of Seven (G7) summit in May.
Mr Kerry toured the Hiroshima Peace Memorial and Museum, whose haunting displays include photographs of badly burned victims, the tattered and stained clothes they wore and statues depicting them with flesh melting from their limbs.
“It is a stunning display. It is a gut-wrenching display,” he said.
“It is a reminder of the depth of the obligation everyone of us in public life carries ... to create and pursue a world free from nuclear weapons,” he told a news conference.
After the tour by Mr Kerry and his fellow G7 foreign ministers, the group issued a statement reaffirming their commitment to building a world without nuclear arms but said the push had been made more complex by North Korea’s repeated “provocations” and by worsening security in Syria and Ukraine.
The ministers from Britain, Canada, France, Germany, Italy, Japan and the United States laid white wreaths at a cenotaph to the victims of the August 6, 1945, bombing, which reduced the city to ashes and killed some 140,000 people by the end of that year.
The highest-ranking US official to have toured the memorial park is Speaker of the House of Representatives Nancy Pelosi, who visited in 2008. Mr Kerry is the most senior executive branch official to visit.
“Everyone in the world should see and feel the power of this memorial,” Mr Kerry wrote in a guest book.
“It is a stark, harsh, compelling reminder not only of our obligation to end the threat of nuclear weapons, but to rededicate all our effort to avoid war itself.”
Asked if this meant Mr Obama should come, Mr Kerry said: “Everyone means everyone. So I hope one day the president of the United States will be among the everyone who is able to come here. Whether or not he can come as president, I don’t know.”
At Mr Kerry’s suggestion, the ministers made an impromptu visit to the Atomic Bomb Dome, the skeletal remains of the only structure left standing near the hypocenter of the bomb explosion and now a UNESCO World Heritage site.
Three days after a US warplane dropped a nuclear bomb on Hiroshima, another atomic bomb was dropped on Nagasaki, on August 9, 1945.
Japan surrendered six days later.
A visit by Mr Obama could be controversial in America if it were viewed as an apology.
A majority of Americans view the bombings as justified to end the war and save US lives, while the vast majority of Japanese believe it was not justified.
Hopes for Obama’s visit to Hiroshima and Nagasaki were raised after an April 2009 speech in Prague when he called for a world without nuclear weapons.