North Korean leader Kim Jong Un will ultimately set the timeline for denuclearization, Secretary of State Mike Pompeo said in an interview in Singapore Friday.

Pompeo made the comments when an interviewer with Channel NewsAsia asked him when denuclearization will take place, pointing out that leaving the process open-ended makes people incredibly nervous. The Trump administration has outlined no timeline of its own for denuclearization. And even though Mr. Trump declared North Korea was no longer a nuclear threat after his meeting with Kim in Singapore, the Washington Post reported earlier this week that North Korea is believed to be constructing new missiles.

Pompeo said the "world should be less nervous" than before the summit.

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"The ultimate timeline for denuclearization will be set by Chairman Kim, at least in part," Pompeo said. "The decision is his. He made a commitment, and we're very hopeful that over the coming weeks and months we can make substantial progress towards that and put the North Korean people on a trajectory towards a brighter future very quickly."

Pompeo's remarks could be concerning for skeptics of North Korea's willingness to denuclearize.

Last month, Pompeo told CNN in a phone interview he would not put a timeline on denuclearization.

"I am not going to put a timeline on it, whether that's two months, six months, we are committed to moving forward in an expeditious moment to see if we can achieve what both leaders set out to do," Pompeo told CNN.

The agreement Mr. Trump and Kim signed in June gave no timeline for denuclearization. Mr. Trump has insisted that good progress is being made with North Korea, and getting along with Kim is a good thing. Earlier this week, Mr. Trump profusely thanked Kim for sending the remains of believed U.S. soldiers home, and said he looks forward to seeing Kim "soon." White House press secretary Sarah Sanders said no further meetings are planned.

Thank you to Chairman Kim Jong Un for keeping your word & starting the process of sending home the remains of our great and beloved missing fallen! I am not at all surprised that you took this kind action. Also, thank you for your nice letter - l look forward to seeing you soon! — Donald J. Trump (@realDonaldTrump) August 2, 2018

Pompeo has become frustrated with questions about denuclearization in the past. In June, he berated a reporter who asked how denuclearization would be verified. At the time, Pompeo had no answer for how the verification process would occur, instead calling a reporter's question "insulting and ridiculous and frankly ludicrous."

Pompeo has been at the front lines of the North Korea negotiations, meeting secretly with top North Korean officials.

When Pompeo traveled there in July, the North Koreans accused him of making "gangster-like" demands on denuclearization, after Pompeo had seemed to suggest the meeting went relatively well.

"If those requests were gangster-like, they are, the world is a gangster," Pompeo said at the time. "There was a unanimous decision at the U.N. Security Council about what needs to be achieved."