U.S. President <a gi-track='captionPersonalityLinkClicked' href=/galleries/search?phrase=Barack+Obama&family=editorial&specificpeople=203260 ng-click='$event.stopPropagation()'>Barack Obama</a> speaks as he attends a joint press conference with South Korean President Lee Myung-Bak at the presidential house on March 25, 2012 in Seoul, South Korea. World leaders are gathering in Seoul to discuss the threat of nuclear terrorism, the recurrence nuclear power plant meltdown and to minimize nuclear material across the world.