On December 26, the Democratic People's Republic of Korea (DPRK) and its southern neighbor the Republic of Korea (ROK) held a ceremony to commence the eventual reconstruction of inter-Korean road and rail links across the peninsula. The ceremony was approved by the United States, who has been eager to maintain pressure on Pyongyang in the hope of achieving denuclearization. Nevertheless, the move wraps up what has been a year of reconciliation and diplomacy concerning Korea.

Averting catastrophe, both states saw rapid warming of ties and many summits between the two leaders. The Demilitarized Zone (DMZ) is being disarmed at a surprising pace, while talk has abounded of formally ending the Korean War and creating a formal peace regime on the peninsula. In the bigger picture, it has been a year that has projected historic potential for the future of Korea.

But will the momentum carry on into 2019? What can we expect? Today's ceremony was notable in the fact that it was purely ceremonial than an act of solid construction. This speaks volumes concerning the obstacles which lie ahead.

What has been achieved so far is but a particle of that has been planned, with so many projects set out in the Panmunjom Declaration ultimately being frustrated by sanctions, a lack of progress on the nuclear issue and Washington's stubbornness in giving leigh way to Seoul.

As a result, save there is a breakthrough, 2019 is likely to pose more challenges than success stories in inter-Korean relations. Unless Washington drastically changes its negotiating position concerning Pyongyang, then not much is likely to happen. The year will thus ultimately hinge on the outcomes of the second leader summit between DPRK leader Kim Jong Un and U.S. President Donald Trump.

“They never do anything without our approval,” tweeted Trump a few months ago in reference to the Republic of Korea (ROK). The statement was rude and patronizing, but it reflected an untimely truth in U.S.-ROK relations. Although Seoul has its own interests, views and differences when it comes to foreign policy concerning Washington, it pays careful attention in its decision making not to upset the United States.

Critics often accuse this as being an act of colonialism. However, the country obtains for itself important strategic benefits on a regional level by ensuring it does not upset its “senior partner”, not least during the time of an incredibly volatile and transactional administration in the White House.

When it comes to inter-Korean relations, however, Seoul is placed in a more precarious position. The United States, being further away geographically and having military advantages, is more confrontational towards Pyongyang, sometimes to the extent of disrespecting Seoul.

Denuclearization forms the bedrock of Washington's policy. On the other hand, being a neighbor of the country and thus an immediate recipient of any consequences, ROK places a greater priority on peace, compromise and co-existence with the DPRK, than pursuing denuclearization as a forthright goal. This has underpinned Moon Jae-in's recent moves in improving ties with the country. Trying to balance both priorities, he has sought to act as a mediator in facilitating dialogue between the two sides, eager to avoid upsetting either party.

However, towards the end of 2018, things have hit a roadblock. The number of things Moon is able to give Pyongyang, such as the resumption of inter-Korean projects on infrastructure, business and tourism, are limited because of sanctions. While Moon believes these activities can help secure peace and co-existence, Washington refuses to budge on sanctions, maintaining its emphasis on denuclearization.

At the same time, Pyongyang is not going to surrender its nuclear program so willingly. While the Blue House understands Pyongyang's point of view, it also recognizes it cannot cross Washington's lines given the inevitable consequences of such an act.

Thus for 2019, if no breakthrough can be found between the U.S. and DPRK, there are problems afoot. Inter-Korean ties are not likely to progress any favor, but freeze as they are and even stagnate. The DPRK is likely to voice its discontent against Seoul and becomes less willing to cooperate, although it is unlikely to return to provocative behavior. Thus, despite most of 2018's events being engineered by Moon's diplomacy, the number of things in his power to save the situation is diminishing quickly.

Therefore, all eyes should turn towards the second Kim-Trump summit, scheduled to take place early in the year. Observers should hope for an increased lenience towards sanctions on Washington's side alongside a greater willingness to make concessions and close nuclear facilities on Pyongyang‘s side.

It is not unreasonable to say that such a meeting will ultimately set the scene for how inter-Korean ties can play out. All initiative, all momentum and progress rest upon this. Otherwise, there's not really much left the DPRK and ROK can do for each other.