The delegates agreed to resume the meeting at 3 pm today South Korean time (0600 GMT, 2 am EDT), said Seoul's presidential spokesman Min Kyung-wook. Min did not disclose any other details about the talks which adjourned at 4:15 am today.
Marathon talks are not unusual for the Koreas, who have had long negotiating sessions in recent years over much less momentous issues.
At the meeting, South Korea's presidential national security director, Kim Kwan-jin, and Unification Minister Hong Yong-pyo sat down with Hwang Pyong So, the top political officer for the Korean People's Army, and Kim Yang Gon, a senior North Korean official responsible for South Korean affairs.
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The meeting came as a series of incidents raised fears that the conflict could spiral out of control, starting with a land mine attack, allegedly by the North, that maimed two South Korean soldiers and the South's resumption of anti-Pyongyang propaganda broadcasts.
On Thursday, South Korea's military fired dozens of artillery rounds across the border in response to what Seoul said were North Korean artillery strikes meant to back up a threat to attack the loudspeakers.
An official from South Korea's Defense Ministry, who didn't want to be named because of office rules, said on Saturday that the South continued with the anti-Pyongyang broadcasts after the start of the meeting and planned to make a decision on whether to halt them depending on the result of the talks.