Ambassador to Malaysia

Nominated by President Barack Obama to serve as Ambassador to Malaysia on July 23, 2013, Yun was confirmed by the U.S. Senate on August 1. As Ambassador, Yun emphasized stronger bilateral ties between the United States and Malaysia in all aspects: security, diplomatic, economic and people-to-people.^[11] During his three-year tenure, President Obama visited Malaysia twice, in 2014^[12] and 2015.^[13] Prior to those trips, the last US president to visit Malaysia was Lyndon B. Johnson in 1966.^[14] During his 2014 visit, President Obama and Prime Minister Najib Razak signed the Comprehensive Partnership Agreement, pledging the United States and Malaysia to work closely together on security, business, education and technology issues.^[15] Yun also inaugurated the Oregon-Sabah Collaborative,^[16] bringing together private citizens, local governments, universities and civil society from the two states to promote educational exchange, forest and wildlife conservation, and business ties.^[17] For his work in this area, Yun received the Individual Achievement Award from the Oregon Consular Corps in 2016.^[18]

Special Representative for North Korea Policy

On October 17, 2016, Yun assumed the office of United States Special Representative for North Korea Policy, heading all coordination and implementation of U.S. policy toward North Korea, especially concerning denuclearization. Concurrently, he held the office of Deputy Assistant Secretary for Korea and Japan, managing relations with America's principal allies in developing a coordinated policy toward North Korea.

Yun was the key diplomat securing the release of American student Otto Warmbier who had been imprisoned in North Korea for nearly a year and a half.^[19] In May 2017, Yun met secretly in Oslo with North Korean officials to gain diplomatic access to the four American prisoners held in Pyongyang. Learning on June 6 that Warmbier had been in a vegetative state for the past 15 months, Yun flew with a medical team on an emergency mission to Pyongyang to secure his immediate release on "humanitarian grounds".^[20] He and the team returned Warmbier to his parents' care in the United States on June 12. While in Pyongyang, Yun also conducted a consular visit with the remaining American prisoners, the first since March 2016.^[21]

As part of the agreement to release Warmbier, the North Koreans demanded $2 million as "repayment for medical expenses." Yun confirmed that he signed a pledge to pay that sum on the direct instructions of Secretary of State Rex Tillerson.^[22] However, Trump said in April 2019 that no money had ever been paid.^[23] In the book The Madman Theory by Jim Sciutto, Yun stated that they started with believing that only Kim Jong Un was unpredictable but they eventually had to accept that Donald Trump was as unpredictable and that they had to be "careful what options you gave him (Trump)" because any option you put out there, he could use. Yun said that the White House was looking at all options however extreme, but it was then-Secretary James Mattis that refused to provide certain options for this reason.^[24]

Special Presidential Envoy for Compact Negotiations

Yun retired from the U.S. State Department on March 2, 2018,^[25] He took positions as Senior Advisor with The Asia Group and the United States Institute of Peace and became a regular analyst on North Korea for CNN. In March 2022 the Biden administration brought him back as Special Presidential Envoy For Compact Negotiations to revive the Compacts of Free Association negotiations with the three strategically important Pacific Island countries of Micronesia, Marshall Islands, and Palau, which had been stalled since December 2020. The COFA agreements were set to expire in 2023 for the first countries and in 2024 for Palau, raising US governments concerns about recent economic overtures from China as the deadline neared. Key issues included economic assistance stemming from historic U.S. nuclear testing on the islands, the continuing presence of U.S. military bases and the ballistic missile test site at Kwajalein Atoll, and climate change mitigation.^[26] Negotiations were successfully completed and 20-year assistance agreements totaling $6.5 billion were signed in May 2023 with Micronesia and Palau and in October with the Marshall Islands. Yun retired as Special Presidential Envoy upon completion of the three agreements.^[27]