Sanctions as prepared now will do no good for either side. I think they need a hard talk and actions if neccessary the same way and language they use. It's not time for playing games and diplomatic zig-zags, it's too serious too and Japan, South Krea will/shall have a major say. Though S. Korea will get a nuke defence belt from America, it will not solve any problems for either sides and therefore we need to enforce an international solution with all consequences. The only thing I can think of at the moment is to give them an ultimatum and if they don't act on it to go to war with instruments depending on their choice.
Probably would be a nightmare. SK would probably hate it, since they'd get the refugees. China too. But weighed against a nuclear NK, possibly selling weapons to the highest bidder, its kind of the lesser of 2 evils isn't it? That's the other thing, since we are providing food and medicine to the NKs, they have more money freed up to use on their weapons programs. Taking away the aid would force them to do something about the starving people right? What I never get is..all these starving countries. Don't they have dirt to farm in? It doesn't take much to grow soybeans, rice or whatever. Can these dictators not even pull that off? They can make a nuclear bomb, but heaven forbid they have any farmers. It's crazy.
It's really just this simple: The world is going to hell in a handbasket and we're all along for the ride. So buckle up, hang on and enjoy the ride. Remember to keep your hands and feet inside the basket for your safety.