The statement by Pyongyang's powerful National Defense Commission, the first explicit denial of the key part of an accord heralded by the South as a mini-breakthrough for the bitter rivals, muddies the prospects for better ties between the Koreas and further belies Seoul's claim that it successfully pushed the North in the talks last week to take responsibility for the blast. North Korea's vague expression of "regret" after three days of talks last week over the South Korean soldiers' injuries, not over laying the mines, allowed the two Koreas to back away from threats of war.