North Korean leader Kim Jong Un, left, and South Korean President Moon Jae-in embrace after signing a joint statement at the border village of Panmunjom. (AP)

South Korea’s president on Monday welcomed the upcoming Singapore summit as a “historic milestone” to ease tensions on the Korean Peninsula but noted that Seoul must be part of any future negotiations with the North, which he said could take years.

The remarks by President Moon Jae-in reinforced South Korea’s view of the talks as another step in an ongoing dialogue with North Korean leader Kim Jong Un rather than a one-time attempt by President Trump to reach a deal over Pyongyang’s nuclear and missile capabilities.

Moon played a key role in keeping alive contacts with North Korea after Trump abruptly canceled the summit late last month, and South Korea has led parallel talks with Kim’s regime over initiatives that include plans to open a quasi-diplomatic “liaison office” in the North.

“The relationship of deep-rooted hostility and the North Korean nuclear issue cannot be resolved in one single action through a meeting between leaders,” Moon said in a statement. He predicted a “long process that could take one year, two years or even longer” to resolve disputes with Kim’s regime.

Moon also said the region cannot “depend just on the North Korea-U.S. talks” and that South Korea must be included in any possible future negotiations that emerge from Tuesday’s summit.

“Inter-Korean talks need to be successfully carried out side by side,” he said.

Moon’s official schedule has him remaining in Seoul during the Singapore talks. He spoke with Trump by phone on Monday, the South Korean presidential Blue House said, in a call lasting 40 minutes.

The issue of a formal declaration to end the state of war was brought up, but there were no further details, including which leader brought it up.

In his remarks, Moon said that he expects the Trump-Kim talks to “become a historic milestone on the path toward peace away from war.” He also cited Kim for taking “decisive, proactive action” such as North Korea’s claims that it destroyed a key nuclear test site last month.

But Moon emphasized the need for North Korea to have a wider dialogue with South Korea and other countries.

“The completion of the process requires sincere efforts by South Korea, North Korea and the United States and continued cooperation from neighboring countries,” Moon said in his statement. “We need a long-term approach to lead the process in a successful manner.”