OMAHA, Neb. (CBS.MW) -- Warren Buffett, celebrated as the "oracle of Omaha," has offered this grim prediction about terrorist attacks on U.S. soil: More lie ahead. Speaking to investors and the media over the weekend at his annual conclave, Buffett conceded that he didn't know when an attack would come, but he said that he was sure there would be one and that it would be "a major nuclear event in this country." "Whether it'll happen in 10 years or 10 minutes, or 50 years...it's virtually a certainty," he told reporters. "We are the No. 1 target."