It is no secret that Syria DOES have WMDS. Syria has the biggest chemical weapons program in the region its something nobody denies exists including Assad himself. With Iraq there was reason to believe Saddam Hussain still had WMDS because in Desert Storm in 1991 he did have them and he expelled the UN weapons inspectors whose job it was to destroy the chemical weapons as part of the ceasefire agreement so I think it was perfectly reasonable to at least suspect Saddam still had WMDS. It doesn't matter of the US knew for sure in advance that Saddam had WMDS or if it was just bad intelligence it doesn't have anything to do with the Syria issue and its not a suspicion Assad has WMDS its a fact and that's whats got people worried. You might not have noticed but the US is doing everything possible to avoid a war with Syria so unless it was a legitimate concern why bring up the issue of WMDS in Syria?
Obama says world must reach climate deal in Paris 'while we still can' (Reuters)
from the article: Report: U.S. warns Syria's neighbors of rogue WMDs after Assad ouster