"We have made steady albeit slow progress, but we've always known this was going to take some time," Pompeo told Fox News in an interview Wednesday. "The relationship between Chairman Kim and President Trump is good. I talk to my counterparts there with some frequency. It doesn't get reported. I'm glad about that; I'm glad we're able to keep that quiet. And so we're making the progress that we need."

Pompeo pointed to the outcome of this week's third meeting between South Korean President Moon Jae-in and Kim, saying it was a "successful engagement" that yielded North Korea's promise to dismantle a missile testing site in front of international inspectors.

"That's a good thing. We're moving forward," he said.

The top US diplomat issued a statement Wednesday that welcomed the commitments made by Kim during the inter-Korean summit in Pyongyang, including his willingness to dismantle a key nuclear facility on the condition the US took reciprocal steps.

Pompeo said the US is willing to "immediately" engage in talks with North Korea through a proposed meeting in Vienna, Austria, between the top US envoy for Pyongyang and North Korean officials, as well as a proposed meeting between himself and North Korean Foreign Minister Ri Yong-ho on the sidelines of the United Nations General Assembly next week.

The negotiations will aim to denuclearize North Korea by January 2021, a timeline Kim has committed to, he added in the statement. (Yonhap)