US President Barack Obama Saturday said North Korea is a "pariah state" whose heavily militarized border with the South marks "freedom’s frontier".

US President Barack Obama Saturday said North Korea is a "pariah state" whose heavily militarized border with the South marks "freedom's frontier".

Obama, who was wrapping up a two day visit to South Korea, said Pyongyang's continued pursuit of nuclear weapons is "a path that leads only to more isolation".

"The 38th Parallel now exists as much as a contrast between worlds as it does a border between nations, between a society that's open and one that is closed," he told American troops in Seoul.

"(It is a border) between a democracy that is growing and a pariah state that would rather starve its people than feed their hopes and dreams."

He said ideals such as freedom, progress and democracy that are held dear in much of the world are "not an accident".

"These are things that have to be fought for... And they've got to be tended to constantly, and defended without fail. And here, on freedom's frontier, they are."

Obama's remarks came as the Korean Central News Agency (KCNA) reported Saturday that leader Kim Jong-Un had urged his soldiers to be ready for "impending conflict with the United States".