Joseph Yun, a former US top diplomat on North Korea, said the abrupt ending to the summit speaks to a "lack of preparation."
"You know, I've been to many summits. Usually they involve so much working level work and in fact an agreement is a foregone conclusion. This time we saw very little preparation and I worried about that. And we talk about Singapore not having substance but at least Singapore will lay foundation. So we were looking at something. And as you pointed out, the administration we're lowering the bar every day and yet they couldn't meet that," he said.
Yun said he thinks the "drama in Washington" might have played a role.
"If you're Kim Jong Un, you're watching this. You know. You're saying is this what he's telling me? That we have a great future, great relations? Is this kabuki or what? You have to think he is -- he is also thinking about stepping back a bit.
See his remarks: