By David Alexander and Mark Hosenball WASHINGTON (Reuters) - A Pentagon spy agency report concluded that North Korea likely has a nuclear bomb that can be launched on a missile, but U.S. defense and intelligence officials cast doubt on Pyongyang's atomic weapons capabilities. Illustrating the high stakes surrounding the escalating tensions on the Korean peninsula, a study by the Pentagon's Defense Intelligence Agency stoked fears that North Korea could be closer to being able to launch a nuclear missile. ...