WASHINGTON (Reuters) - Two U.S. B-1 bombers carried out a training exercise on Tuesday with Japanese and South Korean military aircraft in the vicinity of the Sea of Japan, the U.S. military said, amid growing tension over North Korea s missile and nuclear programs. It was first time U.S. Pacific Command B-1B Lancers have conducted combined training with Japanese and South Korean fighter aircraft at night, the U.S. military said in a statement.  