President Obama has warned North Korea to stop its pursuit of nuclear weapons or risk further isolation. Mr Obama, who is in South Korea for the G-20 summit, attended a Veterans Day ceremony with American troops in the capital Seoul to commemorate the Korean war of the 1950s. He said the United States will never stop supporting South Korea's security and that Washington's alliance with Seoul was stronger than ever. He said Pyongyang's nuclear programme has set it on a path of confrontation.