"Should there be a provocation (by the North), the previous agreements will naturally be nullified," Lee said, as quoted by the media outlet.
The latest agreement with Pyongyang on the reduction of armaments along the border does not mean that Seoul is giving up on national defense, the prime minister noted.
"Arms reduction is something reciprocal. This can't be done unilaterally … I can't understand why the agreement not to conduct firing drills and maneuvers would mean giving up on national defense," Lee said in response to the opposition’s claims that the agreement is equal to giving up South Korean defense.
On September 18-20, South Korean President Moon Jae-in and North Korea’s leader Kim Jong-un held their third inter-Korean summit, during which the two sides reached a number of agreements regarding Pyongyang's military and nuclear facilities, as well as the connection of Korean roads and railways.
Pyongyang and Seoul also signed an accord aimed at enhancing mutual trust.