Transcript for White House warns of potential Syria chemical attack

Details continue to come in. More on this from our military analyst Stephen ganyard and our new senior attorney correspondent Ian Pannell. You spent many years in Syria and know the Assad regime well. We don't know the intelligence behind this warning from the white house but do know Assad has done it before. We do know he's done it dozens of times before according to many analysts. Assad has defied conventional logic. Applying the kind of analysis saying why would he do it because president trump has struck before and the because of the psychological impacts they have and secondly because he can. There's only been one response in the past and that was effectively limited. That air base was back in action within hours. The big question, obviously a statement like that designed to deter Assad. Will it work? That's a very good question. I mean, if people believe that president trump will respond again and will have to ratchet up that response, then you've got to conclude that Assad will have to pause, will have to think about whether he will go through with that threat. Let's talk about the possible response now from Stephen ganyard in Tokyo this morning and, Steve, last time we saw a relatively limited strike as Ian was saying, if the white house were forced to strike again would it have to expand? George, it's just going to depend on the message president trump wants to send of the he could keep it limited. Remember last time we saw they just hit aircraft but if they doesn't believe Assad is getting the message he could expand it and include military headquarters. The presidential palace or even Assad himself. The more you expand the targets, the more you run the risk of a possible could applicant with Russia as well, though. That's true. So we've used cruise missiles in the past because it doesn't put U.S. Crews at risk but the Russians have a very sophisticated surface-to-air missile system. In Syria it could conceivably knock down U.S. Cruise missiles. If that happens, excuse me, it risks a direct u.s./russian military confrontation. Okay. Stephen ganyard, Ian Pannell, thanks very much.

This transcript has been automatically generated and may not be 100% accurate.