"[The Syrian government] is the only one that possesses chemical weapons agents and the means of their delivery in a sufficient quantity," she said Saturday.
Some members of Congress have received classified intelligence briefings, presumably including evidence the Obama administration knows it needs to provide if it’s to win congressional authorization for the use of US military force in Syria.
But publicly, at least, the White House has yet to make its case in any detail, and its latest comments haven’t clarified things.
On Sunday, White House chief of staff Denis McDonough said a "common-sense test" rather than "irrefutable, beyond-a-reasonable-doubt evidence" makes the Syrian government responsible.
"We've seen the video proof of the outcome of those attacks,” Mr. McDonough said on CNN’s “State of the Union.”
“All of that leads to a quite strong common-sense test irrespective of the intelligence that suggests that the regime carried this out,” he said. “Now do we have a picture or do we have irrefutable beyond-a-reasonable-doubt evidence? This is not a court of law and intelligence does not work that way. So what we do know and what we know the common-sense test says is [Assad] is responsible for this. He should be held to account."
Part of the problem for President Obama is that showing US evidence in greater detail could reveal sources and methods of intelligence gathering – a problem all administrations have faced over the years, whether it has to do with signals gathering and code breaking, satellite photos, or spies on the ground.