At a nuclear summit in Seoul today, U.S. President Barack Obama aimed a tough message at North Korea and its new leader, calling on the country to dial back its nuclear program. But much like Iran—another country targeted by Obama at the summit—the true scale of North Korea’s nuclear program remains frustratingly opaque.

North Korea is one of the most secretive countries in the world, and when it comes to the country’s nuclear program, Pyongyang keeps its cards close to its chest. What little available evidence there is, however, suggests that the country’s nuclear arsenal is limited in size and sophistication—at least, for now. But developments like North Korea’s upcoming rocket launch, which is slated for mid-April to coincide with the 100th anniversary of founder Kim Il-sung’s birth, threaten to bring the country closer to fully operational nuclear-power status—a step that would pose a great threat to North Korea’s neighbors as well as the United States.

Right now, the only thing the outside world knows for certain about North Korea’s nuclear program is that Pyongyang possesses plutonium that could be made into bombs. U.S. security analysts say that North Korea probably has about 30 to 50 kilograms of separated plutonium, enough for at least six nuclear weapons. Estimates vary, however, depending on how one calculates the efficiency of North Korea’s plutonium production and bomb-making technology. Analyses range from amounts that would be adequate for anywhere from 4 to 12 bombs.

North Korea claims to have converted the fissile material into nuclear weapons. But it’s widely believed that the country has yet to master the technology to miniaturize nuclear warheads so they could be mounted on missiles. Many experts believe North Korea needs at least another nuclear test to make a nuclear weapon small and light enough to shoot on a missile. “Knowing how many tests it took other countries to get a workable warhead, it seems logical to conclude that North Korea would also require at least another test,” said Mark Fitzpatrick, director of the nonproliferation and disarmament program at London-based International Institute for Strategic Studies.

What is even less certain is how far North Korea has come in enriching uranium, which is another way to obtain material for nuclear weapons. The outside world got its first glimpse of North Korea’s uranium-enrichment program when Pyongyang showed a U.S. academic delegation, including Stanford University professor Siegfried Hecker, a modern centrifuge plant at its nuclear complex in Yongbyon in November 2010.

North Korea claimed that the plant was operational and that it was producing low-enriched uranium, which is used as fuel for civilian nuclear reactors that generate electricity. Hecker has said that although he could not confirm that the plant was functional, Pyongyang’s claim was also not inconsistent with what he saw.

If North Korea has indeed acquired the technology to produce low-enriched uranium, it can be assumed that Pyongyang can also produce weapons-grade uranium for making bombs. Scientists say centrifuges that can enrich uranium to 3 percent to 5 percent concentration of uranium-235 that is needed for civilian nuclear programs can easily be converted to produce highly enriched uranium for bombs, which have concentrations of over 90 percent.

Furthermore, the revelation of the centrifuge plant in Yongbyon has led experts to conclude that North Korea must have at least another facility at a separate location in the country. “The fact that they were able to set up and equip the 2,000 centrifuge plant in a short time … is pretty clear evidence that they have to have had a pilot plant somewhere else,” Fitzpatrick said. It remains possible that the hidden pilot plant is being used for producing highly enriched uranium, he added. North Korea set up the centrifuge plant in Yongbyon in a period of 19 months between April 2009, when it kicked out international inspectors from the country, and November 2010, when the U.S. delegation visited the site.

A rocket launch like the one North Korea plans next month would help the country obtain more data about long-range missiles that could be used to carry nuclear warheads. While North Korea insists that the planned launch is intended to put a satellite into space, the United States says that the technology is the same as a missile test and that Pyongyang would be violating a bilateral agreement reached on Feb. 29 that bans the country from such a launch.

If what happened after North Korea’s last rocket launch in 2009 is any clue, tensions would likely escalate. Many worry Pyongyang may follow up the rocket launch with a nuclear test, as it did in 2009. If so, North Korea could move closer to obtaining the technology and confidence for developing a nuclear warhead that is small enough for missiles—a nightmare situation for the U.S. and its Asian allies alike.