Seoul had proposed holding talks on August 19 to discuss family reunions for those separated by the 1950-53 Korean War and other issues of "mutual interest".
Pyongyang has yet to respond shown, but has continued a string of rocket tests -- most recently yesterday when Pope Francis arrived in Seoul for a five-day visit.
"The recent series of missile launches... That threatens our country and our people are intolerable, and will only deepen (the North's) isolation in the international community," Park said in a speech to mark the August 15 anniversary of Korea's liberation from the 1910-45 Japanese occupation.
The North insists that the missile tests are necessary to boost national defence in the face of joint army drills conducted by Seoul and Washington.
The two allies are set to start Monday another joint military drill -- the annual Ulchi Freedom Guardian -- which Pyongyang warned would push the peninsula "to the brink of war.