"False peace offensive of North Korea failed, the Northerners try to change our attitude with threats," Jeong said, as quoted by Yonhap.
He added that Seoul regards peace initiatives of Pyongyang as blatant propaganda.
"It is important that North Korea takes clear measures to refuse from nuclear weapon," Jeong said.
Last month, Pyongyang urged Seoul to accept its offer to hold military talks and called for joint steps to carry out measures for national unity, citing the need to ease tensions on the Korean peninsula. South Korea rejected the proposal, demanding "a real turn" toward denuclearization.
Tensions over North Korea's nuclear and ballistic missile programs escalated after Pyongyang said on January 6 that it had successfully carried out a hydrogen bomb test and put a satellite into orbit on February 7. The moves violated UN Security Council resolutions, and prompted the United Nations as well as the United States to impose sanctions.