Talks between the Republic of Korea and the Democratic People's Republic of Korea have been ploughing ahead in stark contrast to the nuclear negotiations running concurrently between Pyongyang and Washington. Whilst nuclear talks have yet to result in any concrete steps towards the full denuclearisation of the peninsula, numerous steps have been made in working-level talks between representatives of both Korean states', most notably, Monday the 15th of October saw an agreement reached to reconnect rail and road links severed during the Korean war. Logistics have either yet to be worked out, or yet to be revealed, but work is expected to start in the next couple of months. This development is a significant step in inter-korean developments since it could allow for more economic cooperation once the Kaesong industrial complex is reopened and the harsh sanctions regimes begin to relax.
The US has voiced opposition to the speed of developments coming out of Korea, suggesting that these developments serve as 'rewards' in exchange for no nuclear progress. These concerns reached a head with a statement from a South Korean minister suggesting some sanctions could be relaxed. The statement was retracted after a comment from US President Trump, suggesting that "South Korea would not lift sanctions on North Korea without U.S. approval."
The conflict of interests is driving a wedge between the two countries. The United States only has one goal, the denuclearisation of the north. Seoul has a more complex set of goals, given their proximity to the DPRK, their focus is more well-rounded and concentrates on all aspects of the relationship. Economic, political, cultural and military developments are important to Seoul since they have no set end-point for ongoing negotiations, the US does. On top of this, Moon Jae-in, the President of the ROK, has a personal incentive to see stronger unity on the peninsula, as the child of North Korean refugees, he has his own emotional reasons to see peace in Korea. Will the divide between Washington and Seoul widen? It's difficult to predict, however with nuclear talks turning up no major results and working-level meetings continuing at a rapid pace, unless Washington changes its view of what 'peace' in Korea will look like, we are likely to see more clashes in the future as calls continue from major regional players to relax sanctions on Pyongyang.
It should be noted that there is a strong anti-Moon Jae-in movement brewing amongst South Korean conservatives who do not believe in the 'fake peace' underway on the peninsula, and so this administration has until 2022 to turn major progress before the Presidential election could overturn the work that has been done so far. What happens next remains to be seen.