Two of the worlds leading experts on chemical weapons not privy to the details of the assessments urged caution.
Jean Pascal Zanders, a senior researcher at the European Union Institute for Security Studies, said that a video broadcast internationally showing the effects of the alleged attack doesnt necessarily comport with a sarin attack. He said it could represent a number of other problems, including drowning.
And there were other possible red flags in the video.
Why only one person? he said, referring to the video showing one patient it said was a victim. Why do I find the hospital setting, again, unlike what I would expect in a case of chemical exposure? Why is the guy foaming in the hospital, considering the rapid action of sarin. Zanders explained that without an antidote, death is possible within one minute after exposure to sarin.
Richard Guthrie, formerly project leader of the Chemical and Biological Warfare Project of the Stockholm International Peace Research Institute, said the number of those affected appears low. He said, for example, the Tokyo underground attacks in 1995 that involved a small amount of sarin resulted in 13 deaths and more than 1,000 wounded.
Any kind of a large-scale attack would have left a lot of dead, and a lot more showing symptoms, Guthrie said.
Even if there was certain sarin contamination, he said the apparent small effect would raise questions about whether it might have been the result of a mistake, a rebel attack somehow damaging a Syrian chemical weapon in transit, or as happened on several occasions in the Iran-Iraq war, a single poorly labeled artillery shell being used accidentally.
Even that would seem to fall short of a red line, Guthrie said.
After Hagels statement, the White House released a letter to McCain and Sen. Carl Levin, D-Mich., chairman of the Senate Armed Services Committee, who on Wednesday had asked Obama for information about Syria.
Our intelligence community does assess with varying degrees of confidence that the Syrian regime has used chemical weapons on a small scale in Syria, specifically the chemical agent sarin, wrote Miguel Rodriguez, the White Houses director of legislative affairs.
Earlier this week, U.S. officials, including Secretary of State John Kerry and White House spokesman Jay Carney, declined to say whether the United States agrees with three major allies Israel, Britain and France that Syria had used chemical weapons. They did an about-face Thursday.
Weve seen the White House do a 180, said Reva Bhalla, a Middle East analyst at Stratfor, a private global intelligence firm.
Bhalla said the White House was under growing pressure to at least acknowledge its allies findings.
Theres no debate about whether Syria has a chemical weapons stockpile. International experts agree that the Assad regime is believed to have hundreds, if not thousands, of weapons filled with chemical agents.
David Lightman and Hannah Allam of the Washington Bureau contributed.