UNITED NATIONS (AP) -- There is a "high probability" that al-Qaida will attempt an attack with a weapon of mass destruction in the next two years, the U.S. government said in a report Monday.
The report to a U.N. Security Council committee monitoring sanctions against the terrorist group did not say where the Bush administration believes such an attack might be launched.
But the United States said it believes that despite recent setbacks, "al-Qaida maintains the ability to inflict significant casualties in the United States with little or no warning."
"The al-Qaida network will remain for the foreseeable future the most immediate and serious terrorism threat facing the United States," the report said. "Al-Qaida will continue to favor spectacular attacks but also may seek softer targets of opportunity, such as banks, shopping malls, supermarkets, and places of recreation and entertainment."
The report said the terrorist organization "will continue its efforts to acquire and develop biological, chemical, radiological, and nuclear (CBRN) weapons."
"We judge that there is a high probability that al-Qaida will attempt an attack using a CBRN weapon within the next two years," it said.
A radiological weapon is a so-called "dirty bomb," which uses traditional explosives to disperse radioactivity. Such bombs could use lower-grade radioactive material which can be more easily produced or obtained than the high-grade uranium and plutonium used for nuclear weapons.
U.S. Defense Secretary Donald H. Rumsfeld said last year that searches of more than 40 sites in Afghanistan used by al-Qaida yielded documents, diagrams and material that showed "an appetite for weapons of mass destruction." But it did not appear al-Qaida had succeeded in making such weapons before the U.S.-led military campaign began in October 2001.
The report said FBI investigations since the Sept. 11, 2001 terrorist attacks "have revealed an extensive and widespread militant Islamic presence in the United States."
"We strongly suspect that several hundred of these extremists are linked to al-Qaida," it said.
The U.S. report also noted that "there are hundreds of ongoing counter-terrorism investigations in the United States directly associated with al-Qaida," primarily on the east and west coasts and in the southwest.
"Identifying and neutralizing these sleeper cells remains our most serious intelligence and law enforcement challenge," the report said.
The activities of the groups identified by the United States center on fund raising, recruitment and training, but "one or more groups or individuals could be used by al-Qaida to carry out operations in the United States or could decide to act independently," it said.
"Al Qaida most likely will use the same tactics that were successful on Sept. 11 in carrying out any future attack in the United States, including efforts by cell members to avoid drawing attention to themselves and to minimize contact with militant Islamic groups and mosques in the United States. They will also maintain strict operational and communications security," the report said.