From the aforementioned 2006 interview:

PBS: [Then-Deputy Secretary of Defense Paul] Wolfowitz and most of those New American Century [neoconservative] people by ’97, ’98, are out there agitating for finishing [what] President George H.W. Bush couldn’t [in Iraq]. … What were you making of those allegations then in the ’90s?

PILLAR: The basic allegation that Saddam’s regime was responsible for all manner of things, including the World Trade Center in 1993 and just about any other terrorism under the sun, … was simply not credible at all. It’s not as if the accusations or the line of argument had been dismissed out of hand; they hadn’t been. … They were looked at carefully, and there simply wasn’t anything there. 

Now, Iraq, of course, was doing other things with regard to sponsorship of terrorism, … and they rightly were on the state-sponsored terrorism list. But what we saw happen after 9/11, trying to put together this thesis of some sort of alliance with Al Qaeda, was a manufactured issue.

PBS: Could you feel that there was among this group, the neocons, that there was a real force out there pushing to overthrow Saddam? 

PILLAR: It was there, but it wasn’t until 9/11 afforded the opportunity by making the American public suddenly much more militant that the prospect of actually going to war became real. Before 9/11, they didn’t have enough to hang on. The desire was there, but the prospect was not. …