President Moon Jae-in's special adviser on unification, diplomacy and security affairs has blamed both North Korea and the United States for the collapse of their second summit in Hanoi last month. 

Moon Chung-in, speaking at a forum held at the Seoul Press Center on Tuesday hosted by the Kwanhun Club, an association of senior journalists, says the U.S. made an excessive demand to North Korea while Pyongyang was overly confident.

He said both sides are responsible for the no-deal summit.

Moon added, however, that he does not believe the summit was a failure, but rather a single frustration in a painful Odyssey-like journey. He warned against viewing the summit as the end of the world and taking extreme measures.

Regarding movements detected in North Korea signaling restoration work at the Dongchang-ri missile launch site, the adviser said it would be a very bad decision to try and use missile activities as leverage in negotiations, and urged Pyongyang to refrain from such actions.

When asked about possible additional sanctions on North Korea, Moon said that sanctions must be justified, and that it's not desirable for the U.S. to impose more sanctions in the absence of a clear provocation by Pyongyang.