The sudden departure of the top U.S. diplomat on North Korea issues underscores persistent divisions in the Trump administration over the value of diplomacy with North Korea.
Joseph Yun, the State Department’s special representative on North Korea policy, confirmed in an email that he is leaving the post but didn’t elaborate on his reasons.
Current and former officials suggested the longtime diplomat would retire in part because he feels he has taken his efforts as far as they can go and lacks the high-profile support from the Trump administration needed to further his diplomacy.
Mr. Yun’s departure, expected on Friday, comes at a critical moment, with North Korea indicating it is willing to talk with Washington and South Korea encouraging the Trump administration to find a way to open a dialogue with Kim Jong Un’s regime.
Differences have surfaced within the Trump administration about the utility of negotiations and what they might achieve, even though tensions appear to be easing on the peninsula.
Mr. Yun and others at the State Department have wanted to enter preliminary discussions with Pyongyang—often called “talks about talks”—as South Korea’s President Moon Jae-in has urged Washington to do.
White House officials, however, want to see meaningful indications that North Korea is prepared to roll back its nuclear arsenal before beginning negotiations and suspects that Pyongyang is still trying to drive a wedge between Washington and Seoul, officials said.
“We want to talk only under the right conditions,” President Donald Trump said at the White House on Monday.
Heather Nauert, the State Department press secretary, attributed Mr. Yun’s departure to “personal reasons.” Secretary of State Rex Tillerson asked Mr. Yun to stay but he demurred, an administration official said.
“We are fully confident that we have terrific, qualified, experienced people who will take this on and continue our maximum-pressure campaign. Our policy has not changed,” Ms. Nauert said. There are no immediate plans for a new special representative to succeed Mr. Yun but officials will search for his replacement once he leaves, she said.
Tensions over North Korea have appeared to ease somewhat after soaring last year, particularly following Mr. Trump’s warning last summer that Pyongyang would face “fire and fury” if it continued to threaten the U.S.
North Korea hasn’t conducted a missile test since late November, and the U.S. and South Korea aren’t expected to resume joint military exercises until April.
Vice President Mike Pence had been prepared to meet earlier this month with North Korean representatives at the Winter Olympics, but Pyongyang canceled the meeting. The Trump administration hasn’t articulated a longer-term approach on talks.
“If the administration is serious about diplomacy, it needs to have the right person doing it and it needs to have a game plan, and it is not clear it has either yet,” said Joel S. Wit, a senior fellow at the U.S.-Korea Institute at Johns Hopkins University and a former State Department official.
“Nobody in the administration has his experience,” Mr. Wit added, referring to Mr. Yun.
South Korea and the U.S. postponed annual springtime military exercises until after the Olympics and Paralympics. Here, South and North Korean athletes march during the Olympic Closing Ceremony. Photo: Yonhap News/Zuma Press
Mr. Yun had been participating in the so-called New York channel of preliminary contact at the United Nations, communicating with North Korea’s envoy there.
An administration official said acting Assistant Secretary of State for East Asian and Pacific Affairs Susan Thornton, who has been nominated to formally take that role, as well as Marc Knapper, the top U.S. diplomat in Seoul, would take on additional responsibilities with Mr. Yun’s departure.
Meanwhile the Trump administration is seeking a nominee to become U.S. ambassador to South Korea, a post that has been vacant since January last year. Last month the White House withdrew its nomination of Victor Cha, a highly regarded Korea expert who served in the administration of George W. Bush. Mr. Cha had spoken out against the idea of a limited military strike on North Korea, a possibility held out by Mr. Trump.
‘Yun was aware that there was little he could do.’
—Go Myung-hyun, a research fellow at the Asan Institute think tank
Mr. Yun, who was born in South Korea and is in his early 60s, had been rumored to be weighing an exit—especially as tensions between the U.S. and North Korea escalated over the past year, said Go Myung-hyun, a research fellow at the Asan Institute think tank in Seoul.
“Yun was aware that there was little he could do,” Mr. Go said.
Mr. Yun, who previously served as ambassador to Malaysia, has been the State Department point person on North Korea since 2016, when he was appointed by President Barack Obama.
Last year, he helped to secure the release of Otto Warmbier, a University of Virginia student who was detained in North Korea for 17 months and died soon after returning to the U.S.
Mr. Yun’s exit is part of a broader exodus of senior experts from the State Department, some by force and some by choice. Michael Ratney, the special envoy to Syria, was pushed out to make way for a political appointee, John Hannah, U.S. officials said. But Mr. Hannah ultimately decided not to take the job and the post remains vacant.
Tom Shannon, the No. 3 State Department official and a career foreign-service officer, recently announced plans to retire once Mr. Tillerson determines his successor. Top officials working on Middle East policy have also left their posts in recent months, and the Trump administration fired several top officials last year when Mr. Tillerson arrived.
—Jonathan Cheng in Seoul and Chris Gordon in Washington contributed to this article.
Write to Felicia Schwartz at Felicia.Schwartz@wsj.com and Andrew Jeong at email@example.com
Appeared in the February 28, 2018, print edition as ‘Top U.S. Envoy for Pyongyang To Depart.’