North Korea accused the United States of spying on the site of an impending rocket launch and threatened Wednesday to shoot down any U.S. planes that intrude into its airspace, Associated Press reported. North Korea says it will send a communications satellite into orbit on a multistage rocket between April 4 and 8. Pyongyang's state radio accused U.S. RC-135 surveillance aircraft of spying on the launch site on its northeast coast, according to South Korea's Unification Ministry, which is in charge of monitoring the North.