North Korea said on Friday it was scrapping all accords with South Korea.
More than more than one million troops face each other across the border there.
The KCNA news agency quoted the Committee for the Peaceful Reunification of Korea as saying:
"There is neither way to improve (relations) nor hope to bring them on track.
"The confrontation between the north and the south in the political and military fields has been put to such extremes that the inter-Korean relations have reached the brink of a war."
The cancellations do not include the armistice at the end of the 1950-53 Korean War, signed by the United States, North Korea and China, but not the South. Technically, the war is not over because there is still no peace accord.
In Washington, the State Department said the US would keep pursuing a 2005 multilateral deal under which Pyongyang agreed to abandon its nuclear programmes.
North Korea exploded its first nuclear device in 2006.
