Top generals from North and South Korea worked to make progress on a long-running border dispute at a second day of high-level talks.
N Korean officers last met their S Korean counterparts in May
Discussions on Tuesday ended early, after North Korea restated its demand that a sea border west of the Korean Peninsula be redrawn further south.
The area lies in rich fishing grounds and has been the scene of bloody naval clashes in the past.
The talks, in the truce village of Panmunjom, are set to last three days.
Military discussions between the two sides have faltered in the past because of the ongoing dispute.
Pyongyang does not recognise the border, known as the Northern Limit Line, which was drawn up by the UN at the end of the 1950-53 Korean War.
"As I said yesterday, there is still difficulty in narrowing differences over the issue of the Northern Limit Line," South Korean Colonel Moon Seong-Mook said.
The area has been a trigger for clashes in the past. Six South Korean sailors were killed in one incident in June 2002.
Col Moon said that Tuesday's talks focused on preventing naval clashes, establishing a joint fishing zone and providing security for cross-border railways and roads.
"There are aspects where some differences of opinion have narrowed and others where there hasn't been much progress," the French news agency AFP quoted him as saying.
"Both sides are trying to reach a compromise or an agreement in this round of talks."
The talks between the generals are the highest-level military dialogue between the two Koreas, who have not signed a peace treaty since the Korean War and remain technically at war.
They come amid a general improvement in ties, with the North finally shutting down its Yongbyon nuclear reactor last week.
The closure was part of an international disarmament deal under which North Korea is to receive energy aid and political incentives in return for ending its nuclear programme.