He was referring to the April 27 inter-Korean summit deal and an accord between US President Donald Trump and the North's leader Kim Jong-un during their Singapore meeting on June 12, both of which call for the "complete denuclearization" of Korea.

"They showed that inter-Korean relations and denuclearization are essentially intertwined. This means a lot to South Koreans," Choi said at the 13th Jeju Forum for Peace & Prosperity underway on this southern resort island.

The leaders effectively sent a message to the world that there won't be a "viable denuclearization process" without moving inter-Korean ties forward, he added.

He stressed the importance of follow-up measures in the coming six months or so, as President Moon Jae-in hopes to have another summit with Kim in Pyongyang this fall.

"We can't have a second declaration repeating the words in the Panmunjom Declaration" he said. "What Cheong Wa Dae is trying to do is to give a sense of stability in the process. Pessimism won't get you anywhere. In that sense, I am either cautiously optimistic and optimistically cautious." Cheong Wa Dae is the Korean name of South Korea's presidential office.

The official reaffirmed the Moon administration's ambition to declare a formal end to the 1950-53 Korean War by the end of this year.

It would open the door for a peace regime on the peninsula, offering a sense of security to people in Pyongyang, Washington and Seoul, he said.

He added Kim needs "political-military benefits," with economic sanctions on his regime "intact, to convince domestic audience that dialogue should go on.

Especially with the suspension of the allies' combined military drills, Kim now has "something to lose" unless he continues to take steps toward denuclearization, Choi pointed out.

It's a strong incentive for Kim to stay in talks, he said. (Yonhap)