The meeting at Panmunjom, where the armistice agreement ending fighting in the 1950-53 Korean War was signed, was the first of its kind on the Korean Peninsula in more than two years. Success will be judged on whether the delegates can pave the way for a meeting between the ministers of each country's department for cross-border affairs. Such ministerial talks haven't happened since 2007.
South Korea has proposed they take place Wednesday in Seoul.
There was still no agreement early Monday morning, more than 15 hours after the delegates began discussions Sunday morning, although South Korean officials earlier seemed confident that they would eventually work out an accord on the ministerial talks.
The South Korean Unification Ministry, which is in charge of North Korea matters, sent reporters a brief text early Monday saying an agreement is being delayed because of an unspecified disagreement over the agenda. But there was no elaboration and it was unclear if a new round of talks would be held Monday.
The intense media interest in the bureaucrats' meeting is an indication of how bad relations between the Koreas have been. Any dialogue is an improvement on the belligerence that has marked the relationship over recent months and years.
Earlier this year, North Korea threatened nuclear war, claimed that the Korean War armistice was void, closed a jointly run factory park and vowed to ramp up production of nuclear bomb fuel. That followed a North Korean nuclear test and long-range rocket launches and, earlier, attacks blamed on the North that killed 50 South Koreans in 2010.
"Today's working-level talks will be a chance to take care of administrative and technical issues in order to successfully host the ministers' talks," one of the South Korean delegates, Unification Policy Officer Chun Hae-sung, said in Seoul early Sunday before the group's departure for Panmunjom.
He said the southern delegation will keep in mind "that the development of South and North Korean relations starts from little things and gradual trust-building."
The delegates in the morning discussed the agenda for the ministerial meeting, location, date, the number of participants and how long they will stay in Seoul, if the meeting is held there, said the Unification Ministry.
Reporters weren't allowed at the venue.
Analysts have expressed wariness about North Korea's intentions, with some seeing the interest in dialogue as part of a pattern where Pyongyang follows aggressive rhetoric and provocations with diplomatic efforts to trade an easing of tension for outside concessions.
If the Koreas can arrive at an agreement for ministerial talks, that meeting will likely focus on reopening the factory park in the North Korean border town of Kaesong that was the last remaining symbol of inter-Korean cooperation, and on other scrapped rapprochement projects and reunions of families separated by the Korean War.
Pyongyang pulled its 53,000 workers from the Kaesong factories in April, and Seoul withdrew its last personnel in May.
Success would also mark a victory for South Korean President Park Geun-hye, who took office in February and has maintained through the heightened tensions a policy that combines vows of strong counter-action to any North Korea provocation with efforts to build trust and re-establish dialogue.
The Koreas have been communicating on a recently restored Red Cross line that Pyongyang shut down during earlier tensions this spring. The site of Sunday's meeting held added significance because the armistice ending fighting in the Korean War was signed there 60 years ago next month. The Panmunjom truce, however, has never been replaced with a peace treaty, leaving the Korean Peninsula technically at war.
Representatives of the rival Koreas met on the peninsula in February 2011 and their nuclear envoys met in Beijing later that year, but government officials from both sides have not met since.
The meeting follows a summit by U.S. President Barack Obama and Chinese President Xi Jinping in California. White House national security adviser Tom Donilon said Obama and Xi found "quite a bit of alignment" on North Korea and agreed that Pyongyang has to abandon its nuclear weapons aspirations.
China provides a lifeline for a North Korea struggling with energy and other economic needs, and views stability in Pyongyang as crucial for its own economy and border security. But after Pyongyang conducted its third nuclear test in February, China tightened its cross-border trade inspections and banned its state banks from dealing with North Korea's Foreign Trade Bank.
North Korea's leader Kim Jong Un late last month sent to China his special envoy, who reportedly told Xi that Pyongyang was willing to return to dialogue. South Korea's Park will travel to Beijing to meet Xi later this month.
The talks between the Koreas on Sunday could represent a change in North Korea's approach, analysts said, or could simply be an effort to ease international demands that it end its development of nuclear weapons, a topic crucial to Washington but initially not a part of the envisioned inter-Korean meetings.
Pyongyang, which is estimated to have a handful of crude nuclear devices, has committed a string of acts that Washington, Seoul and others deem provocative since Kim took over in December 2011 after the death of his father, Kim Jong Il.