Officials also tell Senate panel that they don't believe any terrorist organization has developed a nuclear device yet.
Two high-level government intelligence experts testified Wednesday that al Qaeda is intent on attacking the United States with a nuclear weapon but has not developed a nuclear device.
In a hearing, Charles Allen, chief intelligence officer for the Homeland Security Department, said there is no doubt that al Qaeda wants a nuclear weapon. But, he told the Senate Homeland Security and Governmental Affairs Committee, "I do not believe that any terrorist organization currently has developed a nuclear device." He said, however, that this capability "could change drastically" with the recruitment of people with knowledge of nuclear materials and design.
His testimony was buttressed by Rolf Mowatt-Larssen, director of the office of intelligence and counterintelligence of the Energy Department. Before Sept. 11, 2001, he said, many in the intelligence community believed it was too hard for terrorists to develop a nuclear bomb.
"We should not, however, assume that the technology of a nuclear weapon is beyond the capability of a terrorist group," Mowatt-Larssen said. "A terrorist group needs only to produce a nuclear yield once to change history."
Both experts plan to testify before the committee later Wednesday to discuss classified material. "We do not yet know when and where they intend to strike us next," Mowatt-Larssen testified, "but past experience strongly suggests that they are seeking an attack more spectacular than 9/11."
Mowatt-Larssen said a global effort must be undertaken to get nuclear materials off the black market and stop global trafficking in them. Senate Homeland Security and Governmental Affairs Chairman Joseph Lieberman, I-Conn., summed up the testimony of both men as sobering.
Matthew Bunn, a nuclear exert at the Belfer Center for Science and International Affairs at Harvard University, said that nuclear stockpile security in Russia "has improved dramatically in the past 15 years" but called for more global nuclear security. He too warned of the threat from a terrorist group.
"This is a real danger," he said. Homeland Security Department's Allen said any terrorist nuclear bomb would lack the sophistication of one developed by a country and be of unknown yield. But, he warned, "A nuclear device of any yield could produce thousands of casualties, significant damage to the infrastructure and render large areas uninhabitable."
Similarly, Senate Homeland Security and Governmental Affairs ranking member Susan Collins of Maine supported that assessment, saying that a 10-kiloton nuclear device in Manhattan's Times Square at noon would result immediately in the loss of half a million lives.