Joseph Yun, right, U.S. special representative for North Korea policy, answers questions from reporters following a meeting with Japanese and South Korean chief nuclear negotiators at the Iikura Guesthouse in Tokyo on April 25, 2017, in this file photo taken the same day. Yonhap

The U.S. State Department officially announced, Friday, Joseph Yun, former U.S. special representative for North Korea, as charge d'affaires ad interim at the U.S. Embassy in Seoul, saying he will work to advance the two countries' mutual interest and "ironclad" alliance.

Yun, who served as the envoy for North Korea from 2016-2018, is set to assume office in South Korea after former Ambassador Philip Goldberg retired earlier this month ahead of incoming President-elect Donald Trump's inauguration, Jan. 20.

His appointment comes as both South Korea and the United States seek to ensure that the bilateral alliance remains robust despite the political turmoil following President Yoon Suk Yeol's short-lived martial law declaration and subsequent impeachment.

"Ambassador Yun will work with the Embassy team and the Republic of Korea's (ROK) government to advance our mutual interests and shared values, as well as our ironclad commitment to the U.S.-ROK Alliance," the department said in a media note, referring to South Korea by its official name.

"The Department of State expresses its great appreciation to Ambassador Yun for his distinguished public service in advancing the values and interests of the United States," it added.

Yun was expected to arrive in Seoul, Saturday, according to sources.

He previously served as ambassador to Malaysia from 2013-2016 and principal deputy assistant secretary for East Asian and Pacific affairs from 2011-2013. He has also served at the U.S. Embassy in Seoul in the past. (Yonhap)