John Kerry became the first U.S. secretary of state to pay his respects at Hiroshima's memorial to victims of the 1945 U.S. bombing. Ministers from Britain, Canada, France, Germany, Italy, Japan and the United States laid wreaths at the site on April 11. (Reuters)

Secretary of State John F. Kerry on Monday said he thought everybody, including President Obama, should visit Hiroshima, after completing what he called a “gut-wrenching” visit to a museum at ground zero in the city where the United States dropped the first atomic bomb, in World War II.

“Everyone means everyone,” Kerry told reporters after diplomats from seven powerful democracies issued a declaration vowing to work for a safer world free of nuclear weapons. “So I hope one day the president of the United States will be among the everyone who should be here.”

Kerry said he did not know whether Obama would make a trip to Hiroshima when he visits Japan next month, as the White House is pondering, so he may have to come as an ex-president. But Kerry promised, “I will certainly convey to him what I saw here and how important it is at some point that he gets here.”

Kerry was in Hiroshima for a two-day session with foreign ministers preparing for a meeting next month of the major industrialized nations in the Group of Seven. But their discussions on the crises of the moment were overshadowed by reminders of past horrors. At the Hiroshima Peace Memorial Museum, Kerry and his fellow diplomats viewed powerful remnants left by the bomb nicknamed “Little Boy”: charred tricycles, melted roof tiles, and mannequins with melting skin.

An illustrated guide to the Hiroshima and Nagasaki nuclear bombings

“Going through this museum was a reminder of the depth of obligation that every single one of us in public life carries — in fact, every person in position of responsibility carries — to work for peace,” Kerry said.

He also took an unprompted swipe at suggestions by Republican presidential contender Donald Trump that Japan and South Korea should get nuclear weapons to defend themselves from aggressive moves by North Korea.

“That is also why any suggestion by any candidate for high public office that we should be building more weapons and giving them to countries like Korea or Japan are absurd on their face and run counter to everything every president, Republican and Democrat alike, has tried to achieve since World War II,” Kerry said, his voice tinged with anger and disbelief.

Japanese Foreign Minister Fumio Kishida was equally blunt when asked about Trump’s suggestion.

“For us to attain nuclear weapons is completely inconceivable,” he said.

Kerry’s final day in Hiroshima was marked by contrasts: sunshine and dark memories, stunned silence and children’s laughter, and, ultimately, a note of optimism.

After spending almost an hour at the museum, Kerry and the foreign ministers laid wreaths of white and pink carnations at a cenotaph that frames an eternal flame and the skeletal ruins of the one dome-shaped building left standing after the August 1945 nuclear blast. They approached the marker past about 800 elementary schoolchildren who cheered and waved flags, in a calculated effort to keep the focus on the future.

The children seemed to lift the spirits of the diplomats after a wrenching hour touring the museum’s gruesome and poignant exhibits. One minute, they were standing grim-faced at the cenotaph. The next, they smiled and bent over to shake hands or hug the young children who approached them with paper leis. As they talked to the children, their backs to the marker, a brisk wind arose and blew several wreaths off their silver mounts, but they were quickly put back into place and secured.

“They were touched and moved and truly impressed and shocked,” said Kishida, a Hiroshima native who emotionally described how his fellow diplomats had extended their visit.

The diplomatic lineup at the wreath-laying ceremony presented a strong image of nations once locked in war with each other and now standing as allies. Kerry stood between Kishida and British Foreign Secretary Philip Hammond. They were joined by foreign ministers from Germany, Italy, France and Canada, as well as the European Union.

Kerry, an optimistic man by nature, said the purpose of his visit was one he hoped North Korea’s leader, Kim Jong Un, would heed.

“We have built out of the ashes of war and that moment of horror an extraordinary relationship that stands as an example to people all over the world of what can be,” Kerry said.

To that end, the diplomats issued four highly detailed joint communiques and declarations reiterating their positions on a wide range of issues and conflicts around the world. They called for nuclear disarmament, beseeched North Korea to abandon its pursuit of nuclear weapons, and decried attempts by terrorist groups to obtain chemical weapons and nuclear explosives.

In the Hiroshima Declaration, they addressed the symbolism of meeting in the city nearly 71 years after the end of World War II, a conflict they said “unleashed unprecedented horror upon the world.”

The effort to ensure “a safer world for all,” they said, “is made more complex by the deteriorating security environment in a number of regions, such as Syria and Ukraine, and, in particular by North Korea’s repeated provocations.”

Kerry and other State Department officials stepped delicately around his visit, straddling the ground between an empathetic acknowledgment of the bomb’s enormous death toll and a focus on the quest for a nuclear-free future.

“While we will revisit the past and honor those who perished, this trip is not about the past,” Kerry said before a meeting with Kishida. “It’s about the present and the future particularly, and the strength of the relationship that we have built, the friendship that we share, the strength of our alliance, and the strong reminder of the imperative we all have to work for peace for peoples everywhere.”