'Firm resolve'

Moon and Kim met on Saturday on the DPRK side of the border village Panmunjom, the second inter-Korean summit in a month after the April 27 summit on the ROK side of the village.

In a nationally televised address on Sunday, Moon confirmed the willingness of Kim and Trump to hold the Singapore summit as scheduled.

Kim "again made clear his commitment to a complete denuclearization of the Korean Peninsula", Moon said in the address, adding that Kim said he's willing to cooperate to end confrontation and work toward peace for the sake of the successful summit with Trump.

Moon also said he told Kim that Trump has a "firm resolve" to end hostile relations with Pyongyang and initiate economic cooperation if Kim implements "complete denuclearization".

"What Kim is unclear about is that he has concerns about whether his country can surely trust the United States over its promise to end hostile relations and provide a security guarantee if they do denuclearization," Moon said.

Gregory Koblentz, associate professor at the Schar School of Policy and Government at George Mason University, said the key outcome of the DPRK-US meeting is to specify what the US and DPRK mean by "denuclearization" and if there is any overlap between these definitions. "If not, then the summit is still in doubt," Koblentz said.

Xinhua contributed to this story.