When North Korea unleashed a blistering screed of propaganda Sunday, saying it could no longer trust any promise of peace by the United States and must instead rely on "tremendous military deterrent," it appeared to signal a grave hardening of the combative government's position.

But a few people, scattered from here to Tokyo and Washington, nodded in knowing approval. They saw the harsh rhetoric as a prickly briar patch obscuring a softer meaning: North Korea had gotten the word, they surmised; it was withdrawing a key obstacle to talks with the United States, a demand for a bilateral nonaggression treaty.

"There's no question that signaled a willingness to compromise," said one of those select few, an intermediary in Seoul who recently held private talks with North Korean officials.

Such are the winks and nods in a shadowy world of back-channel contacts underway to resolve the dispute between the United States and North Korea over the North's nuclear program. An informal network of academics, lower-level officials, consultants and intermediaries in several countries is attempting to nurture a secret diplomacy to keep the nuclear impasse from drawing the United States into its next war.

Their meetings do not take place at cloak-and-dagger rendezvous spots. More often, the efforts are pursued over cafeteria coffee at academic conferences with such titles as "East Asian Security Implications."

Some analysts expressed optimism that their efforts could break the rigidly deadlocked positions of the United States and North Korea, from which neither side appears ready to publicly climb down. Others are not so sure. "I've seen a multiple of back channels to North Korea. None of them produced anything of substance," said a former State Department official in Washington, now out of government but still in touch with Korean issues.

"The North Koreans are adroit at using them to build political support," he said. "But when the direct channel, the official contact, starts, all of that warm fuzzy feeling evaporates very quickly."

Now, however, there is no official channel. The United States and North Korea are at an impasse, each refusing the other's conditions for opening talks.

In recent weeks, the closest thing to official talks has involved U.S. special envoy Jack Pritchard and Han Song Ryol, North Korea's deputy U.N. ambassador, who met with little publicity in New York on March 31.

Another contact occurred at the University of California at Berkeley last month. A North Korean diplomat and two North Korean scholars received unusual approval from the U.S. government to attend an academic conference put on by a Canadian research group. To dampen publicity and allow for quiet discussions, the sessions were held behind closed doors.

An even more unusual conference took place in Pyongyang two weeks ago, the first in which South Korean academics were allowed to present position papers at a North Korean meeting.

The papers were "sanitized" of provocative language to avoid controversy before they were presented to 150 North Korean officials and academics in the ornate People's Cultural Palace, according to one participant. But "behind the curtains," in private meetings, South and North Koreans tried to hammer away at the issues that divided them.

"Their message was that they are ready to start a dialogue with the U.S., but not in the open," said Park Myung Lim, a professor of Korean studies at Yonsei University in Seoul who has longstanding contacts with North Korean officials.

Among the messages the South Koreans delivered in return was that North Korea's demand for a nonaggression treaty with the United States was meaningless.

"Our side was telling them it was just a piece of paper," said Moon Chung In, a professor at Yonsei University who shuttles often between the Koreas and United States. Six days after the conference ended, the North's Foreign Ministry issued its blustery statement that -- the South Koreans believe -- signaled flexibility on that demand.

There are other signs of diplomatic activity. Yoon Young Kwan, South Korea's foreign minister, traveled to Washington March 26 with what was reported to be a "road map" for restarting negotiations with North Korea.

One source in Seoul said the plan "was to tell the United States that the law-and-order approach doesn't work. We need more carrots-and-stick approach."

A source in Washington familiar with State Department deliberations said one of those carrots was the idea of a summit between South Korean President Roh Moo Hyun and North Korean leader Kim Jong Il in Pyongyang, an idea U.S. officials discouraged, he said.

"Efforts are underway to make things happen," one State Department official said. "But we're not even at a point yet where there's a formula to discuss."