US Secretary of State Mike Pompeo voiced hope Friday for a second summit between the US and North Korea "before too long," but added there was still work to do.

Both sides have floated the possibility of a second meeting between US President Donald Trump and North Korean leader Kim Jong-un to move forward negotiations to dismantle the regime's nuclear weapons program.

Following an impasse over what denuclearization entails, the talks appeared to be back on track this week, helped largely by a third summit between South Korean President Moon Jae-in and Kim.

"I'm hopeful that I get a chance to travel again to Pyongyang to continue these negotiations before too long," Pompeo said in an interview with MSNBC. "And then before too long ... I hope the two leaders get together again to continue to make progress on this incredible important issue for the entire world."

In a separate interview with Fox News, the top US diplomat said the conditions would need to be right.

"We're working on it. But there's still a little bit of work to do left to make sure the conditions are right and that the two leaders are put in a position where we can make substantial progress," he said.

Trump and Kim held their first summit in Singapore in June.

At that meeting, the first between a US and North Korean leader, Kim committed to work toward "complete denuclearization" of the Korean Peninsula in exchange for security guarantees from the US.

Speaking to a socially conservative group in Washington, Pompeo recalled a trip to Pyongyang in the run-up to the summit that secured the release of three American detainees in the North.

"Far and away the greatest highlight to date of my job as secretary of state was bringing home three Americans from captivity in North Korea," he said, adding it still made him emotional to speak about it.

"Even as we sit here today in this beautiful hall, there are thousands of Christians and people of other faiths in North Korea and around the world like Kim Dong-chul who are praying for deliverance from captivity and from fear of persecution," Pompeo said, referring to one of the three men.

The North's release of the three Korean-American men was seen as a gesture of goodwill ahead of the summit. (Yonhap)