President Yoon Suk Yeol moved quickly to fill the seat of his national security adviser following Kim Sung-han’s abrupt resignation amid speculation of planning faux pas involved in the upcoming state visit to the U.S.

The president named Ambassador to the U.S. Cho Tae-yong as the new security adviser on Wednesday, while first vice foreign minister Cho Hyun-dong has reportedly been tapped as the new ambassador to the U.S.

Kim stepped down following media reports quoting ruling camp insiders speculating blunders with Washington in the process of  fine-tuning details of President Yoon’s visit to the U.S., that caused a possible delay in preparations.

His resignation also came in the wake of a much criticized South Korea-Japan summit, with pundits accusing the president of making excessive concessions while gaining little over key diplomatic, defense and business issues through his discussions with Prime Minister Fumio Kishida.  

Previously, the top office replaced a presidential foreign affairs aide as well as a presidential protocol secretary ahead of the Washington summit amid reports of critical issues arising in the preparatory discussions.