Trump and Kim had their first summit in Singapore in June and agreed to work toward complete denuclearization of the Korean Peninsula in exchange for security guarantees for Pyongyang.

But the sides soon hit an impasse over U.S. demands for more concrete denuclearization steps and North Korean insistence on sanctions relief and other concessions.

U.S. Director of National Intelligence Dan Coats renewed skepticism over the denuclearization pledge this week, saying it is unlikely the North will completely abandon its nuclear arsenal due to the leaders' belief that it is critical to regime survival.

In apparent response to that, Trump tweeted Wednesday that he saw a "decent chance" of denuclearization.

"We made tremendous progress with North Korea," he said Thursday. "When I came in, or let's say at the end of the last administration, frankly, it looked like we were going to war with North Korea. Now, there's no missile testing, there's no rocket testing, there's no nuclear testing."

U.S. Secretary of State Mike Pompeo said Wednesday that he has dispatched a team to lay the groundwork for the next summit, which is to happen "some place in Asia."

Hanoi and Danang, both in Vietnam, have been cited as potential sites.