Nuclear terrorist attack would 'change our world' : U.S. President Barack Obama

At the end of a nuclear security summit in Washington, U.S. President Barack Obama makes a push for increased intelligence-sharing to prevent extremist attacks. Rough Cut (no reporter narration). U.S. President Barack Obama says recent statements made by Republican presidential candidate Donald Trump about South Korea and Japan show he doesn't know much "about the world, generally." Rough Cut (no reporter narration).
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