"We made clear that it would be difficult for us to proceed with the rice aid as scheduled [starting in late May] unless North Korea acts to fulfill the February 13 agreement," Chin Dong-Soo, chief South Korean delegate, told journalists in Pyongyang, North Korea’s capital.
He said the North's compliance with the nuclear deal was "the key" for receiving the rice aid.
The two sides were originally scheduled to wrap up the four days of talks in Pyongyang with a joint statement on Saturday, but the talks were extended until Sunday as the two sides haggled over food aid and nuclear disarmament.
Seoul suspended its massive shipment of rice after the North's missile tests last July.
Ties soured further after Pyongyang's October nuclear test, but improved when the North returned to six-nation nuclear disarmament talks.