President Barack Obama says the world has a shared responsibility to ask how to prevent the suffering that took place in Hiroshima more than 70 years ago from happening again.

Obama spoke today at Hiroshima Peace Memorial Park in Japan, making him the first U.S. sitting president to visit the city since the U.S. dropped an atomic bomb in 1945. Obama then spoke briefly with some Hiroshima survivors.

The president was in Japan for the G-7 summit, which ended today with the leaders of seven rich economies issuing an action plan for countering terrorism and other risks to peace and global growth.

The G-7 leaders say they claim a "special responsibility" for beefing up policies to stimulate and sustain growth of their sluggish economies.

On the sidelines of the talks, the U.S., EU and Japan reiterated their determination to reach agreement on various trade agreements meant to expand mutual market access.

AP wires were used in this report