Keeping diplomatic developments coming at a head-snapping pace, the South Korean government said on Sunday that North Korea's leader, Kim Jong-un, had told President Moon Jae-in that he would abandon his nuclear weapons if the United States agreed to formally end the Korean War and promise not to invade his country. The apparent concessions from the youthful leader were widely welcomed as perhaps the most promising signs yet of ending a standoff on the Korean Peninsula frozen in place since fighting in the Korean War ended 65 years ago.