Officially, the United States and North Korea barely speak to each other, their communications often limited to public exchanges of insults.

The U.S. ambassador in Seoul is "a villain, a crazy person," a North Korean diplomat says. North Korea is a "wasteland" compared to South Korea, President Obama tells the United Nations.

But out of the limelight, and sometimes in secret, a small corps of former U.S. diplomats and intelligence officials, often working with academic specialists, meet regularly with high-ranking North Koreans. They have sat down in Singapore, Berlin, Beijing and elsewhere to discuss everything from the details of North Korea's nuclear program to concerns about the effects of international trade sanctions on Pyongyang. They have talked about the growing security fears in Washington, Seoul and Tokyo, and about the timing of North Korean missile tests.

If it's not quite diplomacy, it sometimes gets pretty close.

"The North Koreans understand that we're in no way representing the United States government. So sometimes, we can raise things that the U.S. government isn't able to," said Leon V. Sigal, a former State Department policy official and long a key player in what are commonly called Track 2 talks. "I can say to them, 'Hey, this is why the U.S. government is doing this.' And then probe and say to them: 'Look, what you're doing is not going to work. How about this?'"

The two countries did quietly hold a series of discussions, apparently late last year, but those came to nothing. Since then, North Korea has staged two nuclear tests and a flurry of missile tests, building an increasingly sophisticated arsenal, but there have been no known direct communications between Washington and Pyongyang.

While Track 2 talks are common between rival countries — Indian academics, for instance, regularly meet with their Pakistani counterparts — the North Korean discussions are often seen as a key part of Washington-Pyongyang relations.

To critics, the Track 2 North Korea meetings are a waste of time. Or worse, they allow Pyongyang to claim the high road — insisting it's seeking an avenue to peace — despite its years of cheating on past deals.

But John Delury, a professor at Yonsei University in Seoul, said that with communication between North Korea and the U.S. almost non-existent, Track 2 talks have become a placeholder for government-to-government discussions. Informal talks are "a way for the North Koreans to send indirect messages," he said, and try out ideas they may be hesitant to suggest in official channels.

While Track 2 participants are rarely formally debriefed by U.S. officials, the substance of their talks is often widely shared among the small pool of experts — in government, academia and think tanks — who focus on North Korea. That information can then be used once official talks restart. "There's a lot that you pick up just by sitting in the same room," ranging from what issues are open to discussion to group dynamics, Delury said.

But what has emerged recently from Track 2 discussions? That depends on who you ask.

To Sigal, the talks have revealed a North Korea willing to discuss limitations on its nuclear weapons program, despite Pyongyang's public insistence that it is now a nuclear power.

"Even now, as bad as things are, it's clear" that North Korea is ready to talk, he said. He declined to spell out the details of his discussions, but said that a series of slow, reciprocal steps by both sides — "they would suspend certain activities, the U.S. would take certain steps" — could lead back to official negotiations.

In the end, he said, those negotiations may not be successful, but: "You don't know until the U.S. and the North Koreans sit down and try to work things out."

Some other Track 2 participants, though, say they've seen no sign of North Korean willingness to discuss denuclearization.

"During several meetings in recent months, I've raised the idea of a denuclearization dialogue with the North Koreans," Evans Revere, a former Asia specialist at the State Department, said in an email. "The response from them has been quite definitive . 'There will be no denuclearization; we are now a nuclear-weapons state; the time for denuclearization dialogue is over; you must learn to live with and accept this new reality.'"

Who is right? It's hard to know. North Korea's policy statements are rarely easy to interpret, with serious proposals sometimes buried inside bombastic propaganda, and experts regularly disagreeing about what message is intended.

Some North Korea watchers, for example, believe that Pyongyang held out an olive branch in July, when a story from the state news agency said the North wanted "the denuclearization of the whole Korean Peninsula." While the statement also included a long list of North Korean demands that would seemingly make any agreement impossible, some saw it as a first offer, and a sign that Pyongyang was willing to start negotiating.

The U.S. government, though, has seen little that looks like an olive branch.

Anna Richey-Allen, the spokesperson for the State Department's East Asia and Pacific Bureau, said Washington is open to talking to Pyongyang. "But the onus is on North Korea to take meaningful actions toward denuclearization and refrain from provocations," she said in an emailed statement.

Years of broken agreements have left much of the world — and much of the U.S. government — unwilling to trust North Korea in negotiations. American officials are deeply hesitant about agreeing to direct talks with Pyongyang, fearing the political fallout if the North again reneges on a deal.

But as Pyongyang's arsenal continues to grow, with experts warning it could have nuclear missiles capable of hitting the United States within a few years, Sigal says the U.S. must focus on those years when North Korea did stand by at least some of its agreements.

"Most people in Washington have an assumption that the North Koreans are bad guys — which is true enough — but also that you can't deal with them. I say that assumption is fundamentally wrong," Sigal said. "I think you have to be talking to them. And that's the purpose of Track 2."