SEOUL - South Korean President Moon Jae In has flatly dismissed the idea of withdrawing US troops from the country if a peace treaty were to be signed to formally end the Korean War, reported Yonhap news agency.

"US Forces Korea (USFK) is a matter of the South Korea-US alliance. It has nothing to do with signing a peace treaty," the president said, according to his spokesman Kim Eui Kyeom.

Kim, a spokesman for the presidential Blue House, was responding to media questions about a column written by South Korean presidential adviser and academic Moon Chung In that was published earlier this week.

The presidential adviser has said it would be difficult to justify the presence of US forces in South Korea if a peace treaty was signed.

"What will happen to US forces in South Korea if a peace treaty is signed? It will be difficult to justify their continuing presence in South Korea after its adoption," the former Yonsei University professor said in an article published on Monday by US magazine Foreign Affairs.

A presidential Blue House official said the adviser's opinions or advice will not necessarily be taken up by the president or his government.

"Special adviser Moon is an adviser on one hand, but on the other hand, he is a professor who enjoys the freedom of thoughts, freedom of speech. The president appointed him as a special adviser to benefit from such ample political imagination in setting the direction of his policies," the official said.

Seoul wants the troops to stay because US forces in South Korea play the role of a mediator in military confrontations between neighbouring superpowers like China and Japan, another presidential official told reporters on condition of anonymity earlier on Wednesday, reported Reuters.

Presidential adviser Moon Chung In was asked not to create confusion regarding the president's stance, Kim said.

The United States currently has around 28,500 troops stationed in South Korea, which North Korea has long demanded be removed as one of the conditions for giving up its nuclear and missile programmes.

However, there was no mention in last week's declaration by Moon Jae In and North Korean leader Kim Jong Un of the withdrawal of US forces from South Korea.

Kim and Moon Jae In pledged to work for the "complete denuclearisation" of the Korean peninsula.

US troops have been stationed in South Korea since the Korean War, which ended in 1953 in an armistice that left the two Koreas technically still at war. The armistice was signed by North Korea, China and the US.