"Yes, they continue to produce fissile material," Pompeo said in response to a senator's question.

But he said "progress is happening" in terms of North Korea's denuclearization. He also called on Kim to deliver on his promise to Trump to work toward the complete denuclearization of the Korean Peninsula.

"We are engaged in patient diplomacy, but we will not let this drag out to no end," Pompeo said, stopping short of offering an alternative. "I emphasized this position in the productive discussions I had with Vice Chairman Kim Yong-chol."

Kim Yong-chol has been Pompeo's counterpart in negotiations to flesh out the summit agreement, which also included Trump's commitment to providing security guarantees to the regime.

Pompeo said there is an "awful long way to go" in the talks and "a great deal of work to do."

But he pointed to a recent report that North Korea has begun to dismantle a key missile testing site in line with Kim's oral agreement during his summit with Trump.

"It's a good thing," he said, noting that Washington is "tracking" the disassembly.

On that report by 38 North, a US website monitoring the regime, which was based on satellite imagery from last week, Trump said Tuesday that "we appreciate that."

And the Trump administration's goals on North Korea have not changed, according to Pompeo.

"Our objective remains the final, fully verified denuclearization of North Korea, as agreed to by Chairman Kim Jong-un," he said, adding later that in terms of a timeline, the administration seeks to achieve it before the end of Trump's first term in 2021, and if possible, before then.

The top US diplomat again urged the international community to strictly enforce sanctions on North Korea to keep pressure on the regime to dismantle its nuclear weapons and ballistic missile programs.

"We absolutely need every single nation to maintain the enforcement of those sanctions to which every nation is committed," he said. "The path ahead is not easy, but our hopes for a safer world -- and a brighter future for North Korea -- endure."

Addressing South Korea's efforts to gain a waiver for certain sanctions on Pyongyang to facilitate dialogue with the North, Pompeo said one request for establishing a military-to-military communication channel between the Koreas has been approved.

The other requests are currently under review, he said. (Yonhap)