BANFIELD: When it comes to Syria's stockpile of chemical weapons, our president has minced no words. If the leader uses them against his own people, he would be crossing a red line, meaning it could trigger U.S. intervention in that civil war. Yesterday, the White House said believes, quote, "with varying degrees of confidence," unquote, that Mr. Assad has used the chemical agent sarin. What is Mr. Obama's next move? Our Barbara Starr is live at the Pentagon now with possibly some of the options. This is a very tricky area. I can only imagine that every single word counts in how we treat this now. Where do we stand?</s>BARBARA STARR, CNN PENTAGON CORRESPONDENT: You're right. Two big words, red line. What does that mean? The president was never really clear about it. The U.S. has no intention at this point of a go-it- alone option in Syria. Nobody is stepping up to the plate as this tragedy for so many continues. Where are we right now, now that the U.S. has said chemical weapons have been used? They want more evidence. The secretary of defense, the White House has said they need better intelligence. Who exactly did it? Think of it as a legal standard of proof that may be very difficult to achieve. But certainly in the 10-plus years since the intelligence debacle in Iraq over their weapons of mass destruction, this time, the White House taking it very slowly and carefully saying, they think it's happened, they have some confidence it's happened, but nobody is looking to take action soon. They're looking to get what they call "more information" -- Ashleigh?</s>BANFIELD: If it's a legal standard of reasonable doubt, there's precedence next door in Iraq. Did not turn out well for Iraq. Who knows if that is going to be the same scenario. Good work, Barbara Starr, and thank you for that. The actor Matt Damon has returned to his hometown. This place is very near and dear to his heart. He has addressed the students of Harvard about what happened at the marathon bombings. You're going to hear first hand what he said, coming up right after the break.
U.S. Says Syria Used Chemical Weapons