U.S. Secretary of Mike Pompeo on Monday said negotiations with North Korea could be “one step forward, one step back,” adding that it was difficult to put timelines on the DPRK’s denuclearization.

During an interview with U.S. media on Monday, Washington’s top diplomat also reiterated that despite setbacks, North Korean leader Kim Jong Un had promised to denuclearize.

“President Trump has made clear that there’s no timeline, that this will be one step forward, one step back, perhaps. But I know we’ve made progress,” Pompeo said.

While Pompeo would not be pinned down on numbers or dates, he added that the current sanctions regime could hasten negotiations.

“I try to be careful when it comes to making predictions about timing. The North Korean people are not doing great under the sanctions regime there,” Pompeo added.

“That, of course, speeds the timeline along and, of course, it’s in America’s best interest to resolve this as quickly as we can.”

Pompeo also indicated that he was hopeful U.S. President Donald Trump and Kim would meet again in the near future.

“I would hope in the coming months our two leaders will be back together when – in a way that we can achieve a substantive first step or a substantive big step along the path to denuclearization,” the U.S. Secretary of State said.

Speaking over the weekend at the National Review Institute’s 2019 Ideas Summit in Washington, Pompeo also gave his opinion on what it was like to negotiate with the North Korean leader.

“From the first time I met him, he was in complete command of the file. He knows exactly the risks, the opportunities, he knows his system. He knows the history of these negotiations,” Pompeo said, according to a State Department readout of the event.

“He also knows that he’s young and wants to make sure that North Korea has a future, and so when he engages with you, he does so in a way that reflects the nature of a long trajectory for North Korea, and that as he knows in his early thirties that he’s got to run this country for some time.”

Pompeo’s comments come as talks between Washington and Pyongyang appear stalled following a failed summit in the Vietnamese capital of Hanoi in February.

A weekend report from Reuters highlighted how during the meeting between Trump and Kim, the U.S. President handed his North Korean counterpart a list detailing all the facilities and aspects of the nuclear program Washington would like to see shut down.

While Pompeo also indicated on Monday that sanctions against North Korea would be maintained, Trump also recently caused confusion about Washington’s own unilateral sanctions against the DPRK.

Trump tweeted on April 22 that he was rolling back a “large-scale” sanctions package against the DPRK, the day after the U.S. Department of Treasury issued two designations against China-based entities dealing with North Korea.

At the time it was unclear which sanctions Trump was referring to, though the new designations from the Office of Foreign Assets Control (OFAC) remain listed on the organization’s website.