Moon Jae-in, the South Korean president, will next week make his first overseas visit since being inaugurated in May, although there are concerns that his summit talks in Washington with President Donald Trump will be overshadowed by differences on trade and, more importantly, security and defense ties.

Quoting White House insiders, US media have reported that Trump was "furious" over the South Korean government's decision to delay the full deployment of the US Army's Terminal High Altitude Area Defense (THAAD) anti-missile system until a thorough environmental impact assessment can be completed.

Trump had previously caused confusion and anger in South Korea by demanding that Seoul cover the cost of the deployment of the system, which is designed to intercept incoming North Korean ballistic missiles. That particular bump in the bilateral relationship was smoothed over by James Mattis, the US Secretary of Defense, who reassured one of Washington's most important security partners that they would not be required to pay for the deployment of THAAD.

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Costs demand

Moon Jae-in will visit Washington on June 29

Moon's administration was mollified, but South Koreans have not forgotten that during his election campaign, Trump repeatedly demanded that South Korea "pick up all the expense" when it comes to defense. Trump has also stated that both Seoul and Tokyo should develop and deploy their own nuclear weapons to defend themselves if they are not willing to pay for a US military deterrent based in Japan and South Korea.

The US president's anger is unlikely to have been assuaged by comments over the weekend by Moon Chung-in, a high-ranking adviser to the South Korean leader, who told correspondents attending a conference in Washington that Seoul should be willing to scale down joint military exercises with US forces if North Korea agrees to freeze its nuclear weapons and ballistic missile programs.

Moon - known as a dove on security issues - also played down the need for THAAD to be stationed in South Korea and suggested that there is no need to deploy US aircraft carrier strike groups, nuclear submarines or strategic bombers in the region.

South Korea's Presidential Blue House was quick to distance itself from the comments and said Moon Chung-in was expressing his personal opinions and were not those of the administration.

"I know Moon Chung-in very well and those are personal views that he has held for a long time, but it is clear they will not have gone over well in the US," said Daniel Pinkston, a professor of international relations at the Seoul campus of Troy University.

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'Less patience for appeasement'

"There is increasingly less patience and appetite for what could be perceived as a policy of appeasement towards North Korea," Pinkston told DW.

Pinkston points out that there have been "major ups and downs" in the alliance between Washington and Seoul down the years, with President Dwight D Eisenhower angered over government corruption in South Korea in the 1950s, John F Kennedy concerned over the democratic principles of the government in Seoul in the 1960s and disagreements over human rights and trade in subsequent decades.

"So there have always been disputes between heads of state of both nations, but those have always been secondary to the underlying national interests, which overlap in so many ways and have always outlasted the individual leaders."

Today, the problem is arguably more intense than in the past due to a deeply unpredictable leader in the US who has made statements that, for the first time, undermine the bilateral security relationship.

Jeff Kingston, director of Asian Studies at the Japan campus of Temple University, agrees that Trump "does not do nuance and detail well, but this is a critical situation, so I can only hope that his advisers are close by at all times and are able to stop him doing damage to the relationship with one of America's most important allies and in a region that is a flashpoint.

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"If things were to go wrong here, they would go wrong very quickly and I believe that Trump has to act with delicacy," Kingston told DW.

As well as THAAD and security, there are other areas where the discussions between Moon and Trump might go badly, Kingston said.

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Full agenda in Washington

"They have a very full agenda and there are a lot more differences between these two leaders than there were under the previous administrations in both countries," he said.

"THAAD is obviously on Trump's mind and he is not as keen on a 'Sunshine Mark II' policy towards Pyongyang," he said, referring to the policy of engagement forged by President Kim Dae-jung in the 1990s.

In contrast, Moon is of the belief that sanctions alone have failed to bring North Korea around and that a dual strategy of engagement and pressure may be more effective. A further consideration is that Beijing is fiercely opposed to the deployment of THAAD in South Korea on the grounds that it would impact China's security. Consequently, Seoul is walking a tightrope of trying to keep its leading economic partner - China - happy at the same time as not offending its most important defense partner, the US.

Pinkston believes that both Moon and Trump may not see eye-to-eye, but may also have bigger domestic agendas to deal with, meaning that the meeting in Washington may simply be used as a chance to meet in person, with contentious issues put off to a later date.