Speaking before a crowd of survivors, their descendants and dignitaries including US Ambassador Caroline Kennedy, the mayor urged US President Barack Obama and others to visit, referring to a proposal made at a ministerial meeting in April of the Non-Proliferation and Disarmament Initiative in Hiroshima.
About 45,000 people stood for a minute of silence at the ceremony in Hiroshima's peace park near the epicentre of the 1945 bombing that killed up to 140,000 people.
The bombing of Nagasaki three days later killed another 70,000, prompting Japan's surrender in World War II.
AP
