SINGAPORE (AP) - Terrorists have little chance of making a nuclear bomb, but governments must remain on guard against the possibility, a top U.S. expert said Friday.
Only about 8 kilograms (17.6 pounds) of highly enriched uranium _ far too little to make a nuclear device _ is believed to have leaked into the global black market, said Mark Fitzpatrick, senior fellow for nonproliferation at the London-based International Institute for Strategic Studies.
"This is the classic low-probability, high-consequence danger that governments must focus a great deal of attention" on, said Fitzpatrick, a former deputy assistant secretary for nonproliferation at the U.S. State Department.
Fitzpatrick was speaking to reporters ahead of the IISS's annual Shangri-La Dialogue, a meeting of defense chiefs and scholars held in Singapore.
A minimum of 20-25 kilograms (44-55 pounds) of weapons-grade uranium would be needed to make an implosion-type nuclear device, while four times that much would be needed to make a much simpler gun-type device, Fitzpatrick said.
Amounts of uranium involved in most clandestine smuggling attempts are typically small, Fitzpatrick said, citing a sting operation on the Russia-Georgia border last year in which 100 grams (3.53 ounces) of uranium was recovered.
"Probably it's not so easy to get hold of fissile material, but that doesn't mean complacency should rule. Maybe it's only the tip of the iceberg," Fitzpatrick said.
Osama bin Laden's al-Qaida network has expressed interest in obtaining nuclear weapons while Iran, considered a major sponsor of Islamic terrorist groups by Washington, is in a deadlock with the West over its refusal to suspend uranium enrichment.
Fears of nuclear weapons technology falling into terrorist hands were also stirred by investigations into the black market network of Pakistani scientist A.Q. Khan.
That incident, in part, prompted the U.N. Security Council to adopt Resolution 1540 in April 2004, requiring all U.N. members to pass laws preventing terrorists and black marketeers from dealing in weapons of mass destruction, the materials to make them, and the missiles and other systems to deliver them.
Fitzpatrick called the resolution a "good start," but said follow-through by states on implementing its requirements has been "weak to the point of negligence."
While such defects must be addressed, the public should not be overly anxious about the possibility of a terrorist nuclear bomb, Fitzpatrick said.
"Is it a kind of a risk that the public should be worrying about day-to-day? I would say not," said Fitzpatrick. "The probability is too low for people to be worrying about and keeping up at night.
"But is it the kind of risk that governments should spend a great deal of attention trying to prevent? Absolutely," he said.