The site of the world's first A-bomb attack echoed with the choirs of schoolchildren and the solemn ringing of bells Friday as Hiroshima marked its biggest memorial yet. At 8:15 a.m. -- the time the bomb dropped, incinerating most of the city -- a moment of silence was observed.

Hiroshima's mayor welcomed Washington's decision to send U.S. Ambassador John Roos to Friday's commemoration, which began with an offering of water to the 140,000 who died in the first of two nuclear bombings that prompted Japan's surrender in World War II.