One of US President Donald Trump's point men on North Korea is retiring later this week.

Joseph Yun, the special representative for North Korea policy at the US State Department, said: “This is my own personal decision...Secretary [Rex] Tillerson has told me he appreciates my service and did not want me to go, but he accepts it reluctantly," he told the Washington Post.

His retirement comes just as the Winter Olympics in Pyeongchang, South Korea, end during which the two Koreas participated as one team in the opening and closing ceremonies.

One the sidelines, South Korean President Moon Jae-in and North Korean leader Kim Jong-un's sister Kim Yo Jong met face-to-face for the first time.

White House adviser Ivanka Trump was among a US delegation at the closing ceremonies after which the North Korean regime said it would be open to talks with the US.

Mr Moon has been speaking about a "sunshine policy" towards their neighbours to the north through more open economic policy, a platform he ran his presidential campaign on last year.

As the newspaper reported, Mr Yun "was the main person in the State Department dealing with the North Korea problem, and he travelled to Seoul and Tokyo frequently to coordinate with the US allies".

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Mr Yun was appointed to his current position in 2016 during the previous administration of Barack Obama and has served the US government for more than 30 years.

He is also leaving the State Department at a time when Mr Trump has yet to nominate a US Ambassador to South Korea that made it past initial review. Victor Cha, who was former President George W Bush's North Korea adviser, was in the running but the administration dropped him as a candidate.

My Yun came into the spotlight when he went to Pyongyang to bring American Otto Warmbier back to the US, the 22-year-old was a University of Virginia student who was held in captivity for 17 months after a tourist visit to North Korea.

North Korea Military Parade Show all 6 1 /6 North Korea Military Parade North Korea Military Parade In this image made from video released by KRT on Feb. 8, 2018, a military parade is held at Kim Il Sung Square in Pyongyang, Thursday, Feb. 8 2018, just one day before South Korea holds the opening ceremony for the Pyeongchang Winter Olympics. (KRT via AP Photo) AP North Korea Military Parade This screen grab taken from North Korea's KCTV on February 8, 2018 shows members of North Korea's military taking part in a parade, with missiles being displayed, in Kim Il Sung Square in Pyongyang. North Korea staged a military parade in Pyongyang on February 8 to mark the 70th anniversary of its armed forces, in a show of strength just a day before the Pyeongchang 2018 Winter Olympic Games open in the South. / AFP PHOTO / KCTV / KCTV / -----EDITORS NOTE --- RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / KCTV" - NO MARKETING - NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO ARCHIVESKCTV/AFP/Getty Images AFP/Getty Images North Korea Military Parade In this image made from video released by KRT, North Korean soldiers march during a military parade in Pyongyang, Thursday, Feb. 8 2018. North Korea held a military parade and rally on Kim Il Sung Square on Thursday, just one day before South Korea holds the opening ceremony for the Pyeongchang Winter Olympics. (KRT via AP Photo) AP North Korea Military Parade In this image made from video released by KRT on Feb. 8, 2018, North Korean leader Kim Jong Un, right, inspects honor guards, along with his wife Ri Sol Ju, center, during a military parade in Pyongyang, Thursday, Feb. 8 2018. North Korea held a military parade and rally on Kim Il Sung Square on Thursday, just one day before South Korea holds the opening ceremony for the Pyeongchang Winter Olympics. (KRT via AP Photo) AP North Korea Military Parade In this image made from video released by KRT on Feb. 8, 2018, North Korean leader Kim Jong Un, center, watches the military parade in Pyongyang, Thursday, Feb. 8 2018. North Korea held a military parade and rally on Kim Il Sung Square on Thursday, just one day before South Korea holds the opening ceremony for the Pyeongchang Winter Olympics. (KRT via AP Photo) AP North Korea Military Parade This screen grab taken from North Korea's KCTV on February 8, 2018 shows North Korean leader Kim Jong Un speaking during a military parade in Kim Il Sung Square in Pyongyang. North Korea staged a military parade in Pyongyang on February 8 to mark the 70th anniversary of its armed forces, in a show of strength just a day before the Pyeongchang 2018 Winter Olympic Games open in the South. / AFP PHOTO / KCTV / KCTV / -----EDITORS NOTE --- RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / KCTV" - NO MARKETING - NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO ARCHIVESKCTV/AFP/Getty Images AFP/Getty Images

Mr Warmbier was released into US custody while he was in a coma. He died a week after his arrival.

The President has had an increasingly tense relationship with Mr Kim and Mr Yun was known for advocating a diplomatic solution to denuclearising the Korean peninsula.

Mr Trump had repeatedly called Mr Kim “Rocket Man” as Mr Kim continued to test missiles dangerously close to US ally Japan last year.

For its part, the United Nations Security Council unanimously passed in December 2017 - including votes from Russia and China who have closer ties to Pyongyang - more sanctions on North Korea, further limiting its oil supplies and slave labour market.

Earlier this week at the Conservative Political Action Conference, Mr Trump announced the "largest ever" sanctions on the country. More than 50 companies, shipping vessels, and trade businesses.

Pyongyang most recently had tested an intercontinental ballistic missile on 29 November that US intelligence officials said would put all of the US mainland within striking range.