Recurrent intelligence reports say al Qaeda terrorist Abu Musab Zarqawi has obtained a nuclear device or is preparing a radiological explosive -- or dirty bomb -- for an attack, according to U.S. officials, who also say analysts are unable to gauge the reliability of the information's sources.
The classified reports have been distributed to U.S. intelligence agencies for several consecutive months and say Zarqawi, al Qaeda's leader in Iraq, has stored the nuclear device or dirty bomb in Afghanistan, said officials familiar with the intelligence.
One official said the intelligence is being questioned because analysts think al Qaeda would not hesitate to use a nuclear device if it had one.
However, the fact that the Defense Intelligence Agency (DIA) has reported the nuclear threat in several classified reports distributed since December indicates concern about it.
A DIA spokesman had no comment.
The Jordanian-born Zarqawi, who last year formally linked up with Osama bin Laden's terror network, is thought to be operating inside Iraq and has specialized in suicide bombings and large-scale vehicle bombings. He had several close encounters in recent weeks with Iraqi and U.S. forces.
Senior U.S. intelligence and security officials said in congressional testimony in February that a terrorist attack with weapons of mass destruction -- nuclear, chemical or biological arms -- is likely. CIA Director Porter J. Goss said such a terrorist strike "may be only a matter of time."
Dirty bombs are made by mixing radioactive material with conventional explosives.
A report by the Commission on the Intelligence Capabilities of the United States Regarding Weapons of Mass Destruction faulted U.S. intelligence agencies for not understanding al Qaeda's unconventional weapons programs in Afghanistan prior to 2001, when U.S. forces helped oust the Islamist Taliban government.
"There are critical intelligence gaps with regard to each al Qaeda unconventional weapons capability -- chemical, biological and nuclear," said the report, made public March 30.
The commission said bin Laden told a Pakistani newspaper reporter in November 2001 that al Qaeda has both nuclear and chemical weapons. The CIA then "speculated" in a report that the terrorist group "probably had access to nuclear expertise and facilities and that there was a real possibility of the group developing a crude nuclear device," the commission report said.
The commission also said U.S. intelligence agencies think development of a radiological bomb is "well within al Qaeda's capabilities."
The reported threat of nuclear terrorism comes amid other intelligence indicating that Zarqawi is planning an attack on the United States. Still other intelligence says Zarqawi was planning a chemical weapons attack in Europe, officials said.
In February, U.S. intelligence and security officials said information showed bin Laden had asked Zarqawi to focus future attacks on targets inside the United States. The threat was contained in a classified bulletin to state and local security officials.