U.S. officials and others who track the nuclear capabilities and internal politics of North Korea say they don't see any indications that Pyongyang is planning an imminent nuclear test, but they caution that after the embarrassment of Friday's failed rocket launch it could move provocatively and quickly to do so.
"We consider it at any time a possibility," said one U.S. official who follows North Korea and who briefed NBC News on condition of anonymity. "Might kind of ruin the party or enhance it", he added, referring to Sunday's celebration of North Korean founder Kim il-Sung's 100th birthday.
The officials and experts who spoke with NBC News on Friday questioned whether the North would want to risk another, far greater embarrassment so quickly after the rocket failure. But if it does conduct a nuclear test, it will be following a long tradition of crisis escalation, they said.
"What surprises me is how quickly this is moving. Things that used to happen in years (in North Korea) are now happening in months," said the second official. "When things start spinning fast, I don’t think that's stable, that's safe. So that's concerning.”
David Phillips of Columbia University's Institute for the Study of Human Rights and a North Korea expert, said the government of Kim il-Un does not have to "go nuclear." It has at least two options if it decides to make noise on the international stage: a renewed attack on South Korean islands or naval vessels, or a nuclear test, he said.
"One would be a serious provocation," Phillips said of the first option; the other would quickly become a "global issue."
U.S., South Korean and Japanese officials and experts note that there have been recent preparations at North Korea’s P'unggye-yok test site that could signal a nuclear test, but said those preparations have not intensified over the last few days.
David Albright of the Institute for Science in International Security said his analysts have been monitoring the site almost daily using commercial satellite imagery, but have detected only some movement of earth at a tunnel, which may or may not be related to a test. Albright agrees that a test would quickly move the North's nuclear program to the forefront of global crises.
One thing that could fuel the crisis, he said, would be for the West, particularly Japan and South Korea, to ridicule the failure of Friday’s satellite launch.
"It makes the North Korean military mad,” said Albright, who has visited Pyongyang and met with senior North Korean officials. “If they feel that they are now perceived as weaker, they may react to re-establish their deterrence capabilities."
That, he says, could lead to a further escalation of tensions in the region.
"It would further lock in the view that North Korea does not intend to give up nuclear weapons and it would greatly worry Japan, which always feels it is in the North Korean bull’s-eye,” he said. “Among the public in both Japan and North Korea, it would greatly stimulate the debate that they should get nuclear weapons."
Particularly worrisome for the U.S., senior security officials told NBC News, is the possibility that North Korea would test more sophisticated weapons designs – hydrogen bombs or so-called "boosted fission" weapons, both with yields that far exceed those of nuclear designs. Either a "boosted fission" weapon or a hydrogen bomb would be expect to have yields in the tens or hundreds of kilotons, or many times greater than the bombs the U.S. dropped on Hiroshima and Nagasaki, Japan, at the end of World War II.
It is also possible the North Koreans could detonate a device fueled by highly enriched uranium (HEU) rather than plutonium, the officials said. . The North Koreans have used plutonium exclusively in the first two tests nuclear in 2006 and 2009.
Any of those tests -- HEU, "boosted fission" or thermonuclear-- would show that the North had more advanced weapons design and development capabilities, they said.
Indeed, U.S. officials said North Korea has done significant research into both "boosted fission" and thermonuclear weapons development in recent years. However, without testing, it couldn't be certain that such a weapon is reliable. One constraint, they said, would be whether the geology around the test site could withstand a test.
One U.S. official also said that U.S. intelligence might not be able to immediately confirm or contradict North Korean claims in the wake of such a test.
"If they do a very high yield test and get into multiple tens of kilotons, and they say it's thermonuclear, unless we have some kind of particulate sampling data, I'm not sure what we're going to say,” said one official. “And their statements could add to the confusion."
Phillips, the Columbia University expert, noted that a North Korean nuclear test could complicate U.S. proliferation priorities. What's more significant, he asked, an Iranian program that has been slogging along or a North Korean program with more than a dozen nuclear weapons, some of which that could have yields in the hundreds of kilotons.
“The Obama administration has been focused on Iran as the primary nuclear threat and proliferator. Many believe that Iran is a rational actor that will serve its own national interest and preserve the regime,” said Phillips. “The same can’t be said about North Korea. Successive generation of leaders in North Korea have shown that they are unpredictable and erratic. The recent satellite launch was designed to burnish the authority of its news leader. Instead its had the opposite effect internationally. ... There is now real risk of a nuclear test, which may now be accelerated by the launch failure and that’s the problem.”
And despite the failure of Friday’s rocket launch, U.S. officials say they expect North Korea to continue trying to develop a missile capability that could deliver a warhead big enough to destroy a U.S. city.
“The intelligence community has assessed for a number of years,” said the first U.S. official, “that this (launch) vehicle would be capable of reaching the continental United States -- beyond Alaska, beyond Hawaii -- with a payload of several hundred kilotons.”