South Korean President Moon Jae-in met US President Donald Trump on 10-11 April 2019 to bilateral relations as well as the future course of their dealings with North Korea. Although both these issues are related, their delineation is also important.

Since Trump assumed charge as president, the US has become more transactional in its relationship with allies. Trump has repeatedly argued that most US allies are "free-riders" in both security and economic domains, and should thus contribute more equally towards the sustenance of the US security commitment. Accordingly, the US has insisted that South Korea should pay more for the maintenance of US troops stationed in Korea.

Until 2018, South Korea contributed US$ 830 million of the total cost to station 2,8,500 troops in Korea. Dissatisfied with this figure, Trump has since pushed South Korea to contribute US$ 924 million. In February 2019, South Korea reluctantly agreed to these revised figures in a cost-sharing deal. However, this has not met Trump's approval, which is evident in his announcement of the deal for the period of a year rather than the usual five year span. The Trump administration has also announced that South Korea will purchase more US military arms and equipment - South Korea is the third largest buyer of military equipment from the US since 10 years ago. In fact, Seoul does not agree with the basic premise supplied by the US - that US forces in Korea are aimed at protecting South Korea - arguing that this is also in fulfillment of US' regional strategy.

For the US, bilateral trade also leaves a lot to be desired, with the US trade deficit increasing by around US$ 10 billion to reach a total of US$ 27.6 billion in 2016 despite the 2012 free trade agreement (FTA). This has in the past led to Trump threatening to walk out of the FTA. Just before the Moon’s visit, the US indicated that it might impose a 25 per cent tariff on auto imports from various countries, including South Korea.

On the geopolitical front, the US finds South Korea lacking in implementing specific policies to target China's rise in the region. South Korea, for its part, has openly denied being part of the Indo-Pacific strategy, and despite US displeasure, co-founded the Asia Infrastructure Investment Bank (AIIB).

Overall, it seems these old allies are gradually moving away from each other, particularly when seen in the light of the US assessment of alliances based primarily on a cost-benefit framework. Although both Moon and Trump had good things to say about their relationship and each other in their joint press conference, the divergence has undoubtedly created unease in South Korea. Moon's visit was also important as this was the first time the leaders were meeting  after a disappointing Hanoi Summit between the US and North Korea. During the Hanoi Summit and afterwards, the US appears to have hardened its position, demanding a "big deal." The US does not want to remove sanctions from North Korea until substantial progress is being made in the process of its denuclearisation. In the joint press statement, Trump talked about the right kind of "small deals." However, since then, the US administration has made in clear on multiple occasions that they are opposed to an "incremental" process towards North Korea’s denuclearisation.

In contrast, the South Korean leadership has argued that the momentum of talks with North Korea must continue. In the context of inter-Korea rapprochement, Moon has indicated several times that he would prefer some easing of sanctions on North Korea. Clearly, South Korea’s approach under the Moon administration has been of a step-by-step method to build trust and connections with North Korea.

Moon made a hurried visit to the US because of the realisation, following the Hanoi Summit, of the Trump administration drifting substantially from the South Korean position on North Korea, and in the hope of a commitment regarding a possible third US-North Korea summit. It was not clear whether, and to what extent, Moon was able to convince Trump of the viability of a step-by-step approach, although he was able to secure a more public US commitment to a third US-North Korea summit.

Overall, although the US and South Korea project an image of close coordination, the reality is that there are increasing limitations to their bilateral relationship, as well as fundamental differences in approach with regard to North Korea. Unless both countries are able to work together seamlessly, the situation will only be to North Korea's advantage. The US must begin by exercising greater caution in their pronouncements on behaviour expected of allies, and bring more nuance to their ambitions of denuclearising North Korea.

Dr Sandip Kumar Mishra is Associate Professor, Centre for East Asian Studies, School of International Studies, JNU, and Visiting Fellow, IPCS.