People watch the news on a television screen at a station in Seoul, South Korea, 07 November 2025. According to South Korea's Joint Chiefs of Staff (JCS), North Korea launched a ballistic missile into the East Sea on 07 November. EPA/JEON HEON-KYUN
North Korea is refusing to answer calls by Seoul to establish contact and putting up barbed wire fences along the military border, something that had not been done since the end of the 1950-53 Korean War, Lee was quoted as saying.
"Inter-Korean ties have become very hostile and confrontational, and in the absence of even the basic level of trust, the North is showing some very extreme behaviour," Lee said, according to Yonhap.
Lee was speaking to reporters on a flight from South Africa, where he attended a G20 summit, to Turkey for the last leg of his trip.
South Korea proposed military talks with North Korea on November 17 to discuss drawing up a clear boundary along the Military Demarcation Line (MDL) to prevent armed clashes along the border which could potentially trigger a wider conflict.
North Korea has not responded or reacted to the proposal.
There have been more than 10 border intrusions by North Korean soldiers this year, some leading to South Korean troops firing warning shots under an established protocol.
Lee said winning peace with North Korea will be a long-term effort, but when a firm peace regime is established, "it would be better" for South Korea and the U.S. to cease joint military drills.
Pyongyang has condemned such exercises by the allies, calling them dress rehearsals for a nuclear war against it. About 28,500 U.S. troops and weapons systems are stationed in South Korea.
(Reporting by Jack Kim; Editing by Christian Schmollinger and Toby Chopra)