What regime poses the greatest WMD threat to the US?
Clearly, the Bush administration:

It now appears that the only place in the world where labs similar to those described by Powell actually exist is here, in the United States. Worse, according to the New York Times, the scientist responsible for the design and construction of the U.S. mobile biological lab is under suspicion by the FBI of using this technology to produce the dry powder anthrax used in the October 2001 letter attack that killed seven Americans. This same scientist was allegedly behind similar "defensive" research that identified anthrax- impregnated letters as an ideal platform for delivering the deadly biological agent.

So, when it comes to the only major biological attack conducted against the United States, the available information points to the likelihood that the attack originated in the United States, using technology and techniques developed as part of a defensive biological weapons program that was a product of bad intelligence about Iraq's biological weapons program. -- Scott Ritter