The Bush administration's claim this week that North Korea appears to have been the supplier of converted uranium to Libya is based on evidence that could just as easily point to Pakistan, a key U.S. ally, as the source, according to analysts and officials familiar with the data.
Two senior staff members on the National Security Council have toured China, Japan and South Korea in recent days to brief top officials that U.S. scientific tests strongly suggest North Korea provided Libya with uranium hexafluoride gas, which can be processed into material for a nuclear weapon. Their trip came as U.S. officials are trying to build a united front with key allies if, as expected, North Korea soon agrees to restart six-nation talks on its nuclear programs.
China and South Korea, in particular, have been skeptical of administration assertions that North Korea has a clandestine uranium-enrichment program. Michael J. Green, the NSC's senior director for Asian affairs, brought a handwritten message from President Bush for South Korean President Roh Moo Hyun, according to reports in Seoul.
The questions raised yesterday about the administration's evidence are significant in light of the controversy over the administration's allegations -- later disproved -- that Iraq had illicit arms. Several experts said the administration has to be careful in making its case to allies, given resulting skepticism.
The administration's case is based on tests conducted on equipment and on hexafluoride gas, known as UF6, surrendered by Libya after it agreed to give up its illicit weapons programs. The New York Times reported yesterday that scientists focused on North Korea as a source through a process of elimination by examining isotope fingerprints and ruling out other countries. The Washington Post reported yesterday on another potential link: a canister obtained from Libya that contained the gas apparently had traces of plutonium produced at Yongbyon, where North Korea has its nuclear facilities.
But the International Atomic Energy Agency, which conducted tests on the materials, has not reached the same finding and believes that the evidence is inconclusive.
Several experts said the process of elimination cited by the Times still left open the possibility of other sources for the uranium -- and did not show that it was converted to UF6 in North Korea. The experts see problems as well with the plutonium test cited by The Post.
IAEA tests on the same container -- using samples taken at the same time the United States took samples last spring -- did not indicate the presence of plutonium, and the United States has not shared the results of its plutonium tests with the international agency. Moreover, the suspect container originated from Pakistan, officials said yesterday. The presence of plutonium indicates that it was in North Korea but there is no way to know the origin of the contents of the cylinder, investigators said.
Indeed, the IAEA, which has been investigating the nuclear smuggling network led by Pakistani scientist Abdul Qadeer Khan, has collected a mountain of conflicting information pointing to both Pakistan and North Korea as Libya's source of uranium.
"In order to come to this conclusion, you need a sample from North Korea and no one has a uranium sample from North Korea," said one official investigating the network and Libya's former programs. "The Pakistanis won't allow any samples of their UF6, either," said the official, who discussed the investigation on the condition of anonymity.
North Korea has natural uranium, but there is no direct evidence that it can convert the material to UF6, a gas state that prepares the uranium for enrichment. Although North Korea is suspected of trying to assemble an enrichment program, U.S. intelligence analysts have differed over when it would be operational. Experts said it would be surprising if North Korea had built a conversion facility.
Libya put out an order in 2003 for 20 tons of UF6 in the hopes of beginning research and development on uranium enrichment. But it received only 1.6 tons from the Khan network, delivered in the metal cylinder, when its program was exposed in 2003.
The IAEA and U.S. intelligence launched investigations into the network and were told by Pakistan that North Korea was the source of the uranium shipment. But Khan's Malaysian-based partner, B.S. Tahir, told U.S. intelligence Pakistan was the source.
Even if North Korea made the uranium gas, some investigators believe it is unlikely that Pyongyang intended to sell it to Libya. They believe North Korea would have sold the material to Pakistan, which then sold it to Libya. Another theory is that North Korea sold raw uranium to Pakistan, which converted it to UF6 and sold it to Libya.
"We can't exclude the possibility that the UF6 was made in Pakistan," said David Albright, president of the Institute for Science and International Security.
But Albright did not discount the possibility that North Korea may have been the source. "That has been a theory since last spring," he said. "What amazes me is why this is coming out again now, and the timing has to make one suspicious that the information is being used to pressure allies to take a tougher line with North Korea."