The group was preparing to make a trip to the North from Wednesday to Friday to arrange diverse joint events to celebrate the declaration adopted by the leaders of the South and North during a summit on June 15, 2000.
"It has become technically difficult to leave for the North since the North's invitation has yet to arrive," an official of the civic group said.
To travel to North Korea, one should get an official invitation from the North and submit it to the unification ministry that handles inter-Korean affairs for approval no later than seven days before his or her trip.
In the April 27 inter-Korean summit, the third of its kind, South Korean President Moon Jae-in and North Korean leader Kim Jong-un agreed to push for joint events involving government, parliament and civic groups to celebrate days deemed to be meaningful to both countries.
South Korea's government earlier formed a task force consisting of government and civic group officials for this year's June 15 celebration. A joint event between the two Koreas was last held in 2008 at Mount Kumgang on North Korea's east coast.
They were supposed to discuss the issue during high-level inter-Korean talks slated for Wednesday, but the meeting was canceled unilaterally by the North as it took issue with ongoing joint air exercises between South Korea and the United States.
The two Koreas remain divided and technically at war as the 1950-53 Korean War ended with an armistice, not a peace treaty.(Yonhap)