Since his election last week, South Korean President Moon Jae-in has repeatedly made clear he wants to improve relations with North Korea. To that end, South Korean officials say their immediate priority is to reopen the lines of communication with them at all.
The biggest obstacle to doing that is the United States, and President Moon is dispatching a new Ambassador to DC. President Trump has made clear that he believes diplomacy has “failed,” and that he would only accept any discussions with North Korea under very limited circumstances, which other officials suggested meant they had to stop materially everything the US finds objectionable.
President Moon is a major supporter of the Sunshine Policy which attempted to improve relations between north and south. That policy had been abandoned by recent governments in South Korea, which have tended to favor the more hawkish stance taken by the US.
While South Korea clearly is free to try to reopen communications without America’s permission, they’re going to have to manage the impact such a move would have on US relations. Managing this, while seeking support from nations learning toward diplomacy, notably China and Russia, will likely be an important part of making that politically viable for Moon.