In June, South Korea had announced it would provide 50,000 tons of rice to the North under the World Food Programme (WFP) to help the country address its worsening food shortages. Its original plan was to complete the delivery by September, Yonhap news agency reported.
However, the North is itself reportedly refusing to accept the aid in protest against the joint military exercises South Korea and the United States conducted last month.
The Unification Ministry has been trying to confirm the North's official stance through the WFP, but no response has been delivered so far.
"Given the time required to actually implement the assistance plan, such as holding consultation between the WFP and the North and securing necessary ships, it appears difficult to complete our initial plan by September," Kim Eun-han, the ministry's deputy spokesperson, told a press briefing.
Earlier, a ministry official was quoted as saying that it takes around three weeks for the first shipment of the promised rice to be ready for delivery.
South Korea's decision to provide the food aid came amid a series of reports on the worsening food security situation in North Korea.
The WFP and the Food and Agriculture Orgsation earlier reported that the North's crop production last year hit the lowest level since 2008, adding that an estimated 10 million people, about 40 per cent of the population, are in urgent need of food.
Inter-Korean relations have remained stalled with North Korea not responding to Seoul's offers for talks, apparently thwarted by a lack of progress in denuclearisation talks between Pyongyang and Washington.
( With inputs from ANI )