In a speech during a celebration of Korea's liberation from colonial rule by Japan, Lee called on North Korea to meet for peace talks.
"Let us, as those directly involved, end our threats against each other and begin discussing an end to this long war," he said, continuing:
In this way, it would be possible to talk about effective measures to stop North Korea's progress in acquiring nuclear weapons capability.
The Korean War effectively ended with an armistice agreement in 1953, but North and South Korea are technically still at war.
Earlier this week, North Korea fired a suspected ballistic missile that landed in the Sea of Japan, and the North also condemned a military exercise that South Korea is to conduct together with the United States this week.
