“Demands” truly being the operative word here. Not only did South Korea insist that North Korea open talks on the status of the dormant joint facility — closed now for more than three weeks — they gave Pyongyang only 24 hours to respond, warning of “grave measures” if the Kim regime didn’t offer a positive response:

After weeks of threatening rhetoric from the North, South Korea on Thursday promised its own unspecified “grave measures” if Pyongyang rejects talks on a jointly run factory park shuttered 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 on Thursday proposed working-level talks on Kaesong and urged the North to respond by noon Friday, warning that Seoul will take “grave measures” if Pyongyang rebuffs the call for dialogue.

In a televised news conference, spokesman Kim Hyung-suk refused to say what those measures might be. Some analysts said Seoul would likely pull out the roughly 175 South Korean managers who remain at the complex.

The demand comes as a surprise, considering that the rhetoric and tensions had cooled a bit over the last couple of weeks. The issue should be more important to the North than the South; Kaesong had been one of their only legitimate sources of hard currency, while South Korea’s economy is healthy with or without Kaesong. However, almost 200 South Koreans remain in the complex, and they have been cut off from food, medicine, and supplies during the closure, which makes the humanitarian issue very acute.

The South wants the North to reopen the crossing so that they can resupply the managers, and so far the North hasn’t addressed the concern at all. In fact, they’ve been blocking access even for those purposes:

North Korea has denied South Korean workers and supplies entry to the industrial zone, located a few miles inside the border, accusing Seoul of using the project to insult its leadership. About 180 South Korean workers have chosen to stay there and are believed to be running out of food and supplies.

So what exactly are the “grave measures,” or “severe measures,” as CNN translated the statement?  No one is really quite sure, but it might be a demand to release the managers and the permanent abandonment of Kaesong:

That’s a big threat to Pyongyang, especially with the sanctions already in place.  The South pays the Kim regime $130 a month per worker in hard currency.  Symbolically, it’s even more significant.  This joint project is the crown jewel in the unification effort, and its abandonment puts an end to any effort to reconcile the North and South.  That would be embarrassing for Pyongyang, especially since 53,000 workers would at least know that they’re not going back to work any longer in that effort.