By Arshad Mohammed and Kiyoshi Takenaka
HIROSHIMA, Japan (Reuters) - John Kerry on Monday became the first U.S. secretary of state to pay respects at Hiroshima's memorial to victims of the 1945 U.S. nuclear attack, describing the museum as a "gut-wrenching" reminder of the need to work for a world free of nuclear weapons.
Kerry also told a news conference that U.S. President Obama wants to visit Hiroshima, but that he did not know if the U.S. leader's complex schedule would allow him to do so when he travels to Japan for a Group of Seven (G7) summit in May.
Following the visit by Kerry and his G7 counterparts, the foreign ministers 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 the worsening security in Syria and Ukraine.
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 reminder of the depth of the obligation everyone of us in public life carries ... to create and pursue a world free from nuclear weapons," Kerry told a news conference.
The ministers from Britain, Canada, France, Germany, Italy, Japan and the United States then laid white wreaths at a cenotaph to the victims of the Aug. 6, 1945, bombing, which reduced the city to ashes and killed some 140,000 people by the end of that year.
While he is not the highest-ranking U.S. official to have toured the museum and memorial park, a distinction that belongs to then-U.S. Speaker of the House of Representatives Nancy Pelosi in 2008, Kerry is the most senior executive branch official to visit.
??"Everyone in the world should see and feel the power of this memorial. 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," the chief U.S. diplomat wrote in a guest book.
After a moment of silence by the ministers, Japanese school children, who had lined the entrance waving flags of all the G7 nations, presented them with leis made of paper cranes, symbolizing peace, in each country's national colors.
At Kerry's suggestion, the ministers also 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 U.S. warplane dropped a nuclear bomb on Hiroshima, another atomic bomb was dropped on Nagasaki on Aug. 9, 1945. Japan surrendered six days later.
Speculation has mounted that Kerry's trip could pave the way for an unprecedented visit to Hiroshima by a sitting U.S. president when Obama attends the annual G7 leaders summit in another Japanese city next month.
The top U.S. diplomat said he would tell Obama how important it was to visit, but that he did not know when the president might do so.
A visit could be controversial in America if it were viewed as an apology. A majority of Americans still view the bombings as justified to end the war and save U.S. lives, while the vast majority of Japanese believe it was not justified.
While saying the White House has not yet decided, a senior U.S. official on Sunday said Obama, who last month visited Cuba, has shown he is willing to do controversial things such as visiting Havana last month.
Hopes for Obama's visit to Hiroshima were raised after his April 2009 speech in Prague calling for a world without nuclear weapons. He later said that he would be honored to visit the two nuclear-attacked cities.
The G7 foreign ministers' trip to the museum and memorial is part of Japan's effort to send a strong nuclear disarmament message from Hiroshima, the world's first city to suffer atomic bombing.
"I think this first-ever visit by G7 foreign ministers to the peace memorial park is a historic first step towards reviving momentum toward a world without nuclear weapons," Japanese Foreign Minister Fumio Kishida said in a statement.
In a separate, detailed statement, the G7 ministers singled out North Korea for sharp criticism, condemning its recent nuclear test and launches using ballistic missile technology.
And in a statement on maritime security, they voiced their strong opposition to provocative attempts to change the status quo in the East and South China Seas, an apparent reference to China, which is locked in territorial disputes with other nations including the Philippines, Vietnam and Japan.
(Additional writing by Linda Sieg and additional reporting by Tim Kelly and Elaine Lies in Tokyo; Editing by Michael Perry and Nick Macfie)