The question, he says, lies elsewhere.
"What I have a lot of questions about is okay, what's our responsibility, what is our response, and what would happen next if we were to launch military strikes," Thornberry says.
He says President Obama's administration has two arguments as to why the U.S. should intervene.
"One is that the president said it was a red line and we've got to back up his credibility, and secondly they say we've got to take action to prevent Assad from using chemical weapons again; that the world has an interest in preventing that from happening," Thornberry says.
But, he says so far the president's administration has not made a convincing argument supporting a U.S. attack.
"Any time our country sends our military to do something, we need to understand that lives could be at stake, and that is absolutely one of the considerations that has to weigh on every one of us."
At this point, Thornberry says he's deeply skeptical about taking action of any kind, but he's not going to make a decision until he sees the resolution Congress will vote on and hears more from the Obama administration during classified briefings.
Those are slated to start Monday when Congress goes back to work.
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