SEOUL - The recent nuclear negotiations between the United States and North Korea were substantive and lasted longer than anticipated, according to a Swedish diplomat who helped arrange the talks.

The upbeat analysis by Swedish Special Envoy Kent Harstedt stands in contrast to that of North Korean diplomats, who blamed Washington for failing to bring new ideas to the early October talks in Sweden's capital.

At an event Wednesday in Seoul, Harstedt said the U.S.-North Korea negotiations lasted "many hours" and were "not interrupted." He said he was "cautiously optimistic" the talks would continue, despite North Korea not accepting Sweden's invitation for follow-up talks within two weeks.

"The DPRK hasn't closed the door for continuation at this point," Harstedt said, using an abbreviation for North Korea's official name. "We don't comment exactly on our dialogue with DPRK. We can just say we have a very good working dialogue with them."

"We also have to bear in mind that this is a very, very sensitive and complicated matter to discuss," the envoy added.

Sweden has acted as an intermediary between the United States and North Korea, since the two countries do not have official diplomatic relations. Though Sweden helped set up the U.S.-North Korean talks, Harstedt said he was not involved in the negotiations.

Immediately after the Stockholm talks, U.S. officials characterized the discussions as "good" and insisted that they want them to continue. But North Korea said it has no intention to engage in "sickening negotiations" until the United States takes unspecified steps to withdraw its "hostile policy."

"I think it's good that both sides expressed themselves afterwards," Harstedt said.

Since the breakdown of the Stockholm talks, North Korea has hinted at a return to major provocations.

Last week, North Korean state media published photos of leader Kim Jong Un riding a white horse up the country's highest mountain while warning of a "great operation to strike the world with wonder." Similar reports have sometimes preceded major policy shifts.

Pyongyang has also issued a veiled threat it may resume nuclear or long-range missile tests -- a move that would risk upsetting the nuclear talks.

North Korea has not conducted a nuclear or long-range missile test since 2017. In 2018, Kim announced a self-imposed moratorium on such tests.

Since May, Pyongyang has conducted 11 rounds of short- or medium-range missile launches. U.S. President Donald Trump has shrugged off the tests, saying short-range missiles do not threaten the United States.

Some analysts view North Korea's moves as evidence Pyongyang believes it is in a stronger bargaining position, especially amid Trump's domestic political troubles and upcoming re-election campaign.

U.S.-North Korea talks have been stalled since February, when Trump walked away from a summit with Kim in Hanoi, Vietnam. The two sides disagreed on how to pace sanctions relief with steps to dismantle North Korea's nuclear program.

Although Trump has been reluctant to relax sanctions unless North Korea agrees to abandon its entire nuclear weapons program, he had signaled increased flexibility ahead of the Stockholm talks, speaking of the need for a "new method" to the negotiations.

It's not clear what Washington was prepared to offer. One possibility: the United States could allow the resumption of inter-Korean economic initiatives such as the Kaesong Industrial Complex and tours to North Korea's Mount Kumgang resort.

Such concessions could provide North Korea much-needed sources of cash without completely dismantling the sanctions regime that Washington has used to pressure Pyongyang.

On Wednesday, North Korean state media signaled Kim may not be interested in such a concession.

During a visit to Mount Kumgang, Kim slammed dependence on South Korea for the operation of the resort, according to the official Korean Central News Agency.

During his visit, KCNA said Kim would like to tear down the "backward" and "shabby" facilities built by the South. It suggested he may try to reopen the facility, regardless of progress in inter-Korean relations.

Amid a warming of relations in 2018, North and South Korea agreed to "normalize operations" at Mount Kumgang when conditions allow. Inter-Korean relations have since worsened, and international sanctions have prevented the resumption of South Korean tours.

South Korean tours of Mount Kumgang were stopped in 2008 after a North Korean soldier shot and killed a 53-year-old tourist who had allegedly wandered into an off-limits area. Since then, the resort has not seen much activity.