His remarks came one day after he held a meeting with US President Donald Trump to explain the outcome of his three-day trip to Pyongyang last week for his third and latest summit with North Korean leader Kim Jong-un, in which Kim agreed to take additional denuclearization steps in exchange for corresponding measures from the United States.

Moon earlier said the corresponding measures could, or should, include a formal end to the Korean War that would provide some security assurances to the North.

Kim committed to complete denuclearization of his country in exchange for security guarantees from the US in his historic summit with Trump, held in Singapore in June.

South Korean officials here have said Moon and Trump had in-depth discussions on what the United States' corresponding measures should be when they met here on Monday, along with when and where Trump will hold his second summit with the North Korean leader.

"The declaration of an end to the war that the South and the North are seeking is a process we must undergo to move toward a peace regime. It is also needed to accelerate North Korea's denuclearization steps," Moon said Tuesday.

He dismissed concerns that the move may weaken the South Korea-US alliance, as well as the rationale for the US to maintain tens of thousands of US troops in South Korea.

"The deployment of US Forces Korea is only an issue that will be decided by the South Korea-US alliance, regardless of a formal end to the Korean War or a peace treaty," he said.

South and North Korea technically remain at war as the Korean War ended only with an armistice, not a peace treaty.

Moon has said a formal end to the war will only be a political declaration and that a peace treaty can be signed only after the North completely denuclearizes.

The South Korean president also stressed the need to support the North Korean economy once conditions are met, saying the North's development too will encourage the impoverished nation to continue down the path to complete denuclearization.

"Peace on the Korean Peninsula will not only contribute to regional security, but it may also lead to co-prosperity of the Korean Peninsula and Northeast Asia," he said.

"Peace will support the economy, and the economy will defend peace," Moon added.

When asked later why he or anyone else should believe that North Korea will in fact give up its nuclear weapons this time, the South Korean president said the North Korean leader realizes he would gain more by giving them up than by keeping them.

"Chairman Kim is young, but he is very honest, frank and respectful to elders. Also, he had a very strong will to develop North Korea economically. And so I believe he sincerely is willing to give up nukes if the US guarantees North Korea's security and supports its economic development," the president told the meeting.

Moon also quoted Kim as saying in their latest meeting in Pyongyang that he is very well aware of consequences he and his country may face if caught deceiving the world about denuclearization.

The South Korean president said the US president too apparently believed in Kim's sincerity, or otherwise he would not consider holding a second US-North Korea summit with Kim.

Moon's presidential office Cheong Wa Dae earlier said Moon and Trump had discussed where and when the second Trump-Kim summit would be held, possibly indicating a three-way summit that would also involve Moon.

Moon said his country will actively support the North's economic development when the communist state denuclearizes.

"When North Korea's denuclearization process is completed or considerably moves down the path to a point of no return and sanctions against the North are lifted, South Korea is willing to actively support North Korea's economic development," he said. "I believe that will not only help North Korea but also help revitalize the South Korean economy and create a new engine for growth." (Yonhap)