"The continuing possibility of terrorist attacks using nuclear, biological, or chemical weapons is an ongoing concern in the national security policy arena in the face of a clear trend among terrorists to inflict greater numbers of casualties. Until the anthrax attacks targeted at selected individuals in the Congress and the media, it was thought that the terrorists most likely to attempt attacks with weapons of mass destruction (WMD) were extremist religious groups and small splinter terrorist cells. Worldwide, the likelihood of terrorists being capable of producing or obtaining WMD may be growing due to looser controls of stockpiles and technology in the former Soviet states specifically, and the broader dissemination of related technology and information in general. The Central Intelligence Agency has reported that it is likely that most terrorists will continue to choose conventional explosives over WMD, but warns that the al-Qaeda network has made obtaining WMD capability a very high priority."
CRS Report for Congress, RL31332