SEOUL, South Korea (AP) — North Korean leader Kim Jong Un grins, just on the verge of a belly laugh, as he grasps the hand of a visiting South Korean official. He sits at a wide conference table and beams as the envoys look on deferentially. He smiles broadly again at dinner, his wife at his side, the South Koreans seeming to hang on his every word.

Kim is used to being the center of gravity in a country that his family has ruled with unquestioned power since 1948, but the chance to play the senior statesman on the Korean Peninsula with a roomful of visiting South Koreans has afforded the auto...