Many called it an impossible task.
But today, at the Nuclear Security Summit he assembled in Washington -- leaders from all 47 countries signed a pledge to ramp up efforts at keeping nuclear materials out of the wrong hands.
So tonight, we ask: Do you think the Nuclear Security Summit will make the world a safer place? Or is this simply diplomatic posturing?
Tell us what you think.
Click HERE to read a full report by Cynthia McFadden and Melia Patria about the U.S. team tasked with finding and securing loose nuclear material around the world.
Embedded below is video of President Obama kicking off the summit.