WASHINGTON (Reuters) - A U.S. intelligence official said on Sunday that the United States had no reason to doubt North Korea had tested an advanced nuclear device.  We have nothing to cause us to doubt that this was a test of an advanced nuclear device,  the official said, speaking on condition of anonymity. North Korea claimed to have tested an advanced hydrogen bomb for a long-range missile on Sunday. The U.S. official said, however, that it would take some time to complete a thorough analysis of the size of the blast and type of device detonated. 
U.S. intel official: No doubt North Korea tested advanced device