“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,” one of the letters said.
US Defence Secretary Chuck Hagel: “We cannot confirm the origins of these weapons”
But it added: “Given the stakes involved, and what we have learned from our own recent experiences, intelligence assessments alone are not sufficient – only credible and corroborated facts that provide us with some degree of certainty will guide our decision-making.”
The phrase “varying degrees of confidence” is normally used to reflect differences in opinion within the intelligence community.
The UN says the Syrian rebels are using sarin gas:
Testimony from victims of the conflict in Syria suggests rebels have used the nerve agent, sarin, a leading member of a UN commission of inquiry has said.
Carla Del Ponte told Swiss TV that there were “strong, concrete suspicions but not yet incontrovertible proof”.
Ms Del Ponte did not rule out the possibility that government forces might also have used chemical weapons.
The US says that:
“We are highly sceptical of any suggestions that the opposition used chemical weapons,” said White House spokesman Jay Carney. “We think it highly likely that Assad regime was responsible but we have to be sure about the facts before we make any decisions about a response.”
So, replacing sarin gas use by armed groups with unusually coloured swans, we get the following:
1. The UN are reasonably sure they have seen a green swan in Syria.
2. The US are reasonably sure they have seen a blue swan in Syria.
3. The UN are open to the possibility that a blue swan may exist somewhere in Syria.
4. The US are reasonably certain that no green swans exist in Syria and that what the UN saw was actually a blue swan.
On my reading – from a purely logical point of view – the strongest claim here is 3, claims 1 and 2 are equally strong and claim 4 is remarkably weak.