North Korea could have developed nuclear warheads small enough to be mounted on ballistic missiles with the help of China or Pakistan, a U.S. expert on nuclear weapons said Tuesday.
"(It) could have transferred from Khan to North Korea, and it could have been China," David Albright, president of the Institute for Science and International Security (ISIS), said at a forum.
Albright was discussing the seizure of a computer in Switzerland in 2007 that contained a modern nuclear bomb design from the network of A.Q. Khan, a Pakistani nuclear scientist who is suspected of having provided uranium-based nuclear technology to North Korea in exchange for missile technology.
Khan provided the nuclear weapons design information which China gave Pakistan in the early 1980s, Albright said at the forum hosted by the Institute for Corean-American Studies.
"Khan also put into its network more advanced designs," Albright said. "We don't know how complete they were. But there were two more sophisticated designs that were in the Khan network. They were found in computers in Switzerland when the Khan network people were busted."
The U.S. assumes that North Korea has extracted enough plutonium to make several nuclear warheads, but not the actual weapons or the small sophisticated warheads that can be loaded on missiles.
"The bottom line is North Korea would think about making it deliverable because in the end, you always want to have credible deterrent," said Albright, a physicist and founder of a Washington-based independent research institute specializing in nuclear technology. "It's not enough to have something that can only be delivered by a truck. I think North Korea is well on its way to be able to develop reliable warheads for its ballistic missiles."
Albright did not preclude the possibility of North Korea having produced nuclear warheads, saying Pyongyang might have obtained the advanced technology to make a warhead with a couple of kilograms of plutonium.The 36 kilograms of plutonium the North has reported to the International Atomic Energy Agency as its entire stockpile could also have been underreported, he said.
"You cannot dismiss the two kilograms per weapons because they could have learned how to do it," he said. "Russian scientists could have provided nuclear weapons assistance to North Korea."
Talks have abounded about the possible influx of nuclear materials and scientists from the former Soviet Union to North Korea after the collapse of the Soviet Union in 1990.
The reported 36 kilograms means up to 18 warheads could be created if the North actually has acquired the technology to make a warhead with two kilograms as was insisted by its scientists, Albright said. The North has been widely believed to have the technology to produce a warhead with up to four kilograms.
On the North's uranium-based nuclear program, Albright said that Pyongyang has not yet produced highly-enriched uranium for nuclear weapons but could do so within years if not stopped.
North Korea late last year said it has "entered the final stage" of enriching uranium to fuel light-water reactors.
"If they are going to make enough fuel for a light-water reactor, they probably need 25,000 centrifuges," Albright said. "For a weapons program, 3,000 is enough. So they say we are going to enrich uranium for a nuclear power reactor. That implies a pretty large enrichment program. And the way we interpret that is they are planning to build centrifuges this decade that will be large enough to contribute to a nuclear weapons program."The scientist said there is a need to contain the North's uranium program as well as the plutonium extracted from the Yongbyon nuclear facilities, which are being targeted by a six-party deal signed in 2005 for the North's nuclear dismantlement.
Multilateral talks, stalled since late 2008, have been idled by the North's nuclear and missile tests early last year and most recently the sinking of a South Korean warship in March blamed on North Korea.
"In the future, it can be more threatening because it can build more weapons and improve their weapons and also sell to other countries," Albright said of North Korea. "So I think it's a growing threat that has to be addressed more openly and directly in the negotiations. Sanctions and interruptions will make it harder for them to succeed."
Satellite images suggest the North recently began construction activity in the area of its plutonium-producing nuclear facilities in Yongbyon, north of its capital Pyongyang, where a cooling tower was demolished in 2008 as part of the six-party process for its denuclearization.
"North Korea may want to increase the capacity or the ability for the reactor to produce plutonium, and a more sophisticated cooling system is necessary if they wanted to do that," Albright said. "The old model has limitations on the power. You see a pretty large construction area. It's larger than you would think they would need to build a simple cooling tower."