Delegations to the fourth inter-Korean military talks at the truce village of Panmunjom wrapped up their first day Tuesday morning earlier than scheduled.

A South Korean delegate said the North Korean contingent suddenly decided to return home after a two-hour meeting in the morning instead of continuing talks until five p-m as previously agreed.

The official didn’t give the exact reasons for the talks’ abrupt closure, but implied the disagreement over the readjustment of the western sea border was to blame.

He said the talks will continue through Thursday.

The two sides are focusing on signing a memorandum of understanding on security guarantees for the pilot operation of inter-Korean railway lines and an emergency military hotline.