South Korea has vowed to take "grave measures" if Pyongyang rejects talks on a jointly run factory park shut for nearly a month.
The park in the North Korean border town of Kaesong is the most significant casualty so far in the recent deterioration of relations between the Koreas. Pyongyang barred South Korean managers and cargo from entering North Korea earlier this month, then recalled the 53,000 North Koreans who worked on the assembly lines.
South Korea's Unification Ministry proposed working-level talks on Kaesong and urged the North to respond by noon on Friday, warning that Seoul will take "grave measures" if Pyongyang rebuffs the call for dialogue.
Spokesman Kim Hyung-suk refused to say what those measures might be. Some analysts said Seoul would be likely to pull out the roughly 175 South Korean managers who remain at the complex.
Mr Kim said South Korea set the deadline because the remaining workers at Kaesong are running short of food and medicine. He said the companies there are suffering economically because of the shutdown.
To resolve deadlocked operations at Kaesong, he said North Korea should first allow some South Koreans to cross the border to hand over food and medicine to the managers. North Korea did not make an immediate response. South Koreans remaining at Kaesong are free to leave, but have been staying to protect their companies' equipment and products.
The demand for talks follows a lull in what had been a period of rising hostility between the Koreas. Pyongyang has recently eased its threats of nuclear war and expressed some tentative signs of interest in dialogue. Its demands, including dismantling all US nuclear weapons, go far beyond what its adversaries will accept, but Washington, Seoul and Beijing have also pushed for an easing of animosity.
The Kaesong complex is the last major symbol of co-operation remaining from an earlier era that saw the Koreas set up various projects to facilitate better ties.
The factory park has operated with South Korean know-how and technology and with cheap labour from North Korea since 2004. It has weathered past cycles of hostility between the rivals, including two attacks blamed on North Korea in 2010 that killed 50 South Koreans.
More than 120 South Korean companies, mostly small and medium-sized clothing and electronics firms, operated at Kaesong before North Korean workers stopped showing up on April 9..