As kabar says in #577, the most direct analogous situation to our attacking the Taliban for sheltering Al Qaeda is probably Israel attacking Lebanon and then Syria for sheltering Hezbullah (how are we supposed to spell that, by the way?). Israel is doing to Lebanon very much what we did in Afghanistan, with the difference that they view the Lebanese government largely as a victim of Syria and Hezbullah, not a primary sponsor or protector (at least not yet).
I think President Bush is emphasizing Syria in his private and public statements based on precisely this logic. I think he's setting the ground work for an Israeli and/or US attack on significant assets in Syria. That would be a very powerful signal to Iran without immediately requiring an all out response from Iran (e.g. trying to stop the flow of oil form the Gulf). I just heard former CIA head James Woolsey on Big Story on Fox saying that we, not Israel, should be striking at Syrian infrastructure for precisely this reason, to knock Syria down a peg and knock back Iran's position in the area by showing them to be basically running a bluff at this point.
Particularly with the rest of the Arab League basically lining up against Hezbullah it might be a tactic to consider. I do believe that the President and Rummy just might have a bit more info about the situation that I do, so I'll leave that decision to them... <g>
The Syrians have been aiding the insurgency in Iraq. The government of Iraq has criticized those actions and asked Syria to cease and desist. We should use that pretext in any attack against Syria and avoid linking it to Hesbullah and the Israeli efforts.