South Korean President Yoon Suk-yeol writes in the guest book after paying respects to Britain's Queen Elizabeth II, at the altar prepared at the British Embassy in Seoul on Friday. (Yonhap)

With his departure planned on Sept. 18, Yoon will first attend Britain's Queen Elizabeth II's state funeral that is slated to take place in London on Sept. 19, according to Kim Sun-han of the national security office.

Joining other world leaders, Yoon will pay tribute to the world's oldest and longest-serving head of state before taking off for New York, where he will attend the 77th UN General Assembly, Kim said.

"Yoon's attendance to the (queen's) funeral comes after a comprehensive consideration of factors, including the historic importance of the bilateral relations of South Korea and Britain, and the great legacy of the queen and her affection toward Korea," Kim said.

At the UN General Assembly, of which the first day of the High-Level General Debate will take place on Sept. 20, Yoon will deliver a keynote speech.

Yoon is also expected to hold bilateral meetings with state heads of other countries, such as Japan and the United States on the sidelines of the UN event.

Tribute to the queen

Yoon made an impromptu visit to the British Embassy in Seoul to pay his respects on Friday.

"Deepest condolences to the people of the United Kingdom for the passing of Her Majesty Queen Elizabeth II. She had a strong belief in the cause of human freedom and left great legacies of dignity," Yoon said in a message posted in English on Twitter on Friday.

"Her kind heart and good deed will remain in our memories."

In another post on Facebook, Yoon lauded the queen as a "defender of freedom" who offered consolation and comfort to the people around the world after World War II.

"Queen Elizabeth II showed of an exemplary leadership that penetrated the tumultuous 20th century and the uncertainties of the 21st century," Yoon said in the Facebook message.

"When the dark times of the World War ended and the door to a new era opened, she offered consolation and comfort to many people around the world as a defender of freedom."

Queen Elizabeth II died at the age of 96 on Thursday, after 70 years on the throne. The funeral for the queen is to be held at 11 a.m. on Sept. 19 at London's Westminster Abbey, according to Buckingham Palace.

The queen will lie in state in Westminster Hall for four days prior to the funeral, for the public to visit and pay their respects.

People view and place floral tributes at the gates of Buckingham Palace, following the death of Britain's Queen Elizabeth II, in London, Sunday. (Reuters-Yonhap)

Yoon will be joining scores of world leaders attending the funeral.

US President Joe Biden was one of the first leaders to announce plans to attend the funeral on Thursday, even before the details had been confirmed.

New Zealand’s Prime Minister Jacinda Ardern and European Commission President Ursula von der Leyen also announced their intentions to attend the funeral.

Japan’s Emperor Naruhito and Prime Minister Fumio Kishida are also expected to go, along with Turkey’s President Recep Tayyip Erdogan, and French President Emmanuel Macron, among many more.

Members of other European royal families including from Belgium, Denmark, the Netherlands, Norway and Sweden will also be present.

Russian President Vladimir Putin will not be attending the funeral but delivered his condolences in a Kremlin statement.

"For many decades Elizabeth II rightfully enjoyed her subjects' love and respect as well as authority on the world stage," the Kremlin said. "Russians respected her for her wisdom.”

The state heads and dignitaries attending the state funeral have reportedly been asked to arrive in the UK on commercial flights, and were also banned from using their own state cars or helicopters due to space restraints.

According to a report from Politico, the invitations sent to foreign dignitaries also asked for only heads of state and their spouses or partners to attend the event.

Elizabeth came to the throne when she was 25, in 1952 when her father, King George VI, died. It was not until June 1953 that she was officially crowned.

She visited South Korea at the invitation of then-President Kim Dae-jung in 1999, and visited Hahoe Village near the city of Andong, to celebrate her 73rd birthday.

South Korea's National Assembly Speaker Kim Jin-pyo sent a letter of condolence to his British parliamentary counterparts, and Andong Mayor Kwon Gi-chang also expressed his condolences.

The coronation for King Charles III will take place at a later date that has yet to be confirmed. Given that it should follow a period of mourning and is also a national event, the coronation can take place after months or even years.

By Jo He-rim (herim@heraldcorp.com)