Kevin Kim, who had been serving as the acting U.S. ambassador to South Korea for roughly two months, has departed the post, further prolonging the lack of a formally appointed American envoy in Seoul. Kim recently informed Korea's Ministry of Foreign Affairs of his departure, diplomatic sources said Wednesday. He is said to have returned to the United States for Christmas and did not return to Seoul. Kim took up the post in October last year and played a key role in coordinating U.S. President Donald Trump's visit to South Korea for the Asia-Pacific Economic Cooperation summit later that month, as well as a bilateral summit with President Lee Jae Myung held on the sidelines of that event. Following Kim's departure, James Heller, the deputy chief of mission at the U.S. Embassy, will serve as charge d'affaires for the time being, the embassy said in a notice posted on its website. "For the time being, Deputy Chief of Mission James Heller is expected to continue close communication with our side as acting charge d'affaires," a foreign ministry official said. The official declined to comment