PANMUNJOM, Korea (AP) – North Korea walked out of military talks with South Korea, ending three days of high-level negotiations Thursday with no agreement amid a lingering dispute over their shared sea border.

“We’ve come to the conclusion that we don’t need these fruitless talks any more,” North Korea’s chief delegate Lieutenant General Kim Yong Chol said at the final session in the truce village of Panmunjom.

General Kim criticized the South for avoiding discussions of what he termed the “illegal” sea border. The frontier was drawn by the United Nations at the end of the 1950-53 Korean War, and Seoul has repeatedly rejected the North’s demands that it be changed.

The issue has been a constant obstacle at military talks between the sides, and the disputed waters that contain rich fishing grounds have previously been the scene of deadly battles in 1999 and 2002.

South Korea’s chief envoy, Major General Jung Seung-jo told General Kim it was “highly regrettable” that the negotiations would end without results.

“Your side continued making this demand even though your side knows very well that our side cannot accept it,” General Jung said, referring to the border issue.

The generals from the North and South left the room after the 40-minute session without shaking hands or setting any date for a next meeting – with Kim appearing red-faced and visibly angry.

The South had called for the two sides to at least reach consensus on less controversial issues, such as opening a hotline between Navy commanders to prevent future clashes in waters off the peninsula’s western coast.

At the start of Thursday’s meeting, the North’s Kim mocked his South Korean counterparts.

“Throughout the past few days, I feel as if I had become a victim of April Fool’s Day jokes,” General Kim said.

General Jung had tried to seek compromise and called for understanding the other side’s position, but General Kim flatly refused and retorted that “it would go against respecting principles and truth if you have to respect and accept anything just because it is the other side’s view.”

This week’s talks are the highest-level dialogue channel between the two militaries, and were intended to follow up on agreements reached in May on setting up a joint fishing area around the contended border and cooperation on security arrangements for joint economic projects there.

Waters around the sea border are rich fishing areas and have been a past scene of deadly conflicts in 1999 and 2002.

The two Koreas have made strides toward reconciliation since a 2000 summit between their leaders, but they remain technically at war because the Korean War cease-fire has never been replaced by a peace treaty.