SEOUL, South Korea (AP) -- President Barack Obama said Tuesday the threat of nuclear weapons remains a potent challenge for the globe to confront, telling foreign leaders that "the security of the world depends on the actions that we take."
Obama, speaking at a nuclear security summit in South Korea, said the international community had made progress in removing nuclear materials and improving security at nuclear facilities around the globe. As a result, he said more of the world's nuclear materials won't fall into the hands of terrorists.
But the president warned "there are still too many bad actors in search of these dangerous materials and these dangerous materials are still vulnerable in too many places."
"It would not take much, just a handful or so of these materials, to kill hundreds of thousands of innocent people and that's not an exaggeration, that's the reality that we face," Obama said.
Obama was seeking to build upon a goal of ridding the world of nuclear weapons despite disagreements with Russia over the next phase of a disarmament program he views as a central part of his foreign policy agenda.
Underscoring the sensitivity of the discussions, Obama told Russian President Dmitry Medvedev that he would have more flexibility after the November election to deal with the contentious issue of missile defense, a candid assessment of political reality that was picked up by a microphone without either leader apparently knowing.
Obama's Republican opponents pounced on the comment, saying the president has a hidden agenda that could include concessions to the Russians if he wins re-election.
On Tuesday, at the start of a session at the summit, Obama was about to sit down when he saw Medvedev two seats away. Obama said: 'Wait, wait, wait, wait,' and then moved to cover up his microphone in jest.
He then enjoyed a hearty laugh with the Russian leader as the two shook hands, a moment captured by photographers and reporters.