The U.S. has used the underground world of back-channel diplomacy before to achieve things with North Korea such as the release of Americans, but most experts are skeptical Pyongyang is ready for serious negotiations about denuclearization.
"There has been historically back-channel dialogues between the U.S. and North Korea, and I think that continues," said Andrew Scobell, a senior political scientist at the Rand think tank in Washington. "Certainly, the Secretary of State [Rex Tillerson] indicated that diplomatic behind-the-scenes activity was continuing. And it is happening, and we'll just have to wait and see what the results are."
The back-channel talks between the U.S. and North Korea have been happening for several months, The Associated Press first reported last week. They included secret talks that led to the release of Otto Warmbier, the American student detained in North Korea who was released by the regime in a coma and later died in the United States.
A State Department spokesperson declined to comment to CNBC this week when asked about the status of any current back-channel talks.
"Back channels are useful tools for sending messages back and forth but they won't be any kind of path forward in terms of setting up negotiations or resolving things," said James Carafano, vice president of foreign and defense policy studies at the Heritage Foundation who advised the Trump transition team on foreign policy and homeland security.
The current back-channel talks are now focused on the so-called New York channel through the United Nations. The key players are Joseph Yun, a former U.S. ambassador to Malaysia and now the U.S. special representative for North Korea policy, and North Korea's senior diplomat, Choe Son Hui, who is head of the Foreign Ministry's North American office.
One of the back-channel meetings led the U.S. to learn Warmbier's condition was dire and that resulted in Secretary of State Tillerson approving the visit by Yun to Pyongyang for a meeting that ultimately led to Warmbier getting released.
"Since that episode, I'm told that the 'New York channel' has been resurrected and there are periodic contacts," said Robert Einhorn, a former State Department official and now Brookings senior fellow who was involved in Oslo, Norway, back-channel talks between North Korea and the U.S.
Einhorn said in interview with CNBC that the New York channel was interrupted about a year ago when the Obama administration imposed sanctions on North Korea for human rights violations, and it also designated the regime's leader, Kim Jong Un, as one of the targeted individuals.
"The North Koreans retaliated by cutting off the New York channel, and what that meant was no official contacts between the United States and North Korea," he said. "And so those contacts resumed this spring in Oslo."
The resumption of contacts also coincided around the time there was change in the South Korean government. South Korean President Moon Jae-in, whose parents were refugees from North Korea, won the presidential election in May and had campaigned on rebooting Seoul's tough approach to Pyongyang.
There was hope in some quarters that the hermit regime might slow down on ballistic missile tests and be open to resume unconditional dialogue that could lead to denuclearization of the Korean Peninsula. But that hasn't happened despite Moon's peace overtures to North Korea for inter-Korean military talks and even his offer in June to have a unified Korean team compete in the 2018 Winter Olympics in Pyeongchang, a South Korean mountainous area less than 45 miles from the demilitarized zone.
At the same time, Tillerson has made it clear several times including this week that the U.S. is willing under the right circumstances to open formal dialogue with Pyongyang to talk about denuclearization of North Korea. Yet only days after that offer the regime's young leader threatened to launch missiles toward the waters off the U.S. Pacific territory of Guam.
"The impression that the U.S. has is that the North Koreans are not eager for such a dialogue,' said Einhorn. "The U.S. has indicated that before talks can begin that the North Koreans would have to take some steps to demonstrate their sincerity."
Indeed, on Tuesday State Department spokesperson Heather Nauert told reporters that the U.S. is "willing to sit down and talk" to the North Koreans but added "that's not going to happen imminently." She added there are still "some serious steps before we get there."
Experts suggest a premature return to negotiations would be unwise and essentially reward bad behavior because North Korea has continued to threaten the U.S. and its Asian allies, even beyond the recent rhetoric about targeting Guam. Also, there's no signs the North is willing to give up its ballistic missiles tests and some believe the regime is preparing to set off its sixth nuclear test.
"The North Koreans have repeatedly and publicly rebuffed the idea of negotiations focused on their nuclear and missile capabilities," Brookings' Einhorn wrote in a blog Monday. "This posture could be designed to postpone talks until they have reached certain programmatic milestones; it could be an effort to stake out a strong bargaining position for eventual negotiations; or it could genuinely reflect an unwillingness to consider any limitations on their strategic programs."
On Wednesday, the Pyongyang's mouthpiece Uriminzokkiri quoted leader Kim as stating "the U.S. should stop at once arrogant provocations against the DPRK and unilateral demands." The regime followed it up Thursday with its state-run news agency KCNA issuing propaganda posters depicting missile attacks on the U.S. mainland, including images of what appears to be missiles striking the U.S. Capitol.
DPRK is a reference to North Korea's formal name, the Democratic People's Republic of Korea.
President Donald Trump also has lobbed warnings recently at North Korea about the use of military force, including "fire and fury" and "locked and loaded" remarks. Even amid the rhetoric on both sides, though, experts say the back-channel talks serve a useful purpose and historically have proven they can clear up misunderstandings and sometimes result in breakthroughs that can avoid outright military conflict.
During the 1960s Cuban missile crisis with the Soviet Union, for example, there were behind-the-scenes talks that were used successfully to get Moscow to remove its offensive weapons in Cuba in exchange for the U.S. dismantling its Jupiter rockets in Turkey. Similarly, there have been back-channel discussions with Iran over the years, including one that eventually led to the nuclear agreement.
In the North Korean situation, though, Carafano said the back-channel talks have "limited utility" and probably won't resolve anything but still are a good thing. "Even during the height of the Cold War with the Soviet Union, we continued to communicate over things because even countries that are totally at odds with each other actually have things to talk about."