Working to gather more evidence against Assad regime: US

The US has said it is working with its allies and the Syrian opposition groups to gather more evidence to establish use of chemical weapons by the Assad regime, based on which a policy decision can be taken.
The White House, in a statement, said although it has been established through " varying degrees of confidence", "much more to be done to verify" the use of chemical weapons.
"We have established with varying degrees of confidence that chemical weapons were used in limited fashion in Syria and the agent is sarin, as we have said. We have some physiological tests that are part of the collection of evidence," White House Press Secretary Jay Carney said.

"But there is much more to be done to verify conclusively that the red line that the President has talked about has been crossed. It is very important that we take the information that's been gathered thus far and build upon it" he said.
The US, he said, is working with the French, British and other allies and partners to gather more evidence.
"Chain of custody is an important issue. Establishing not just that there was an incident of chemical weapons used, but how the exposure occurred, under what circumstances, who specifically was responsible, and again, the chain of custody, how the incident itself was brought about," he said.

Carney said the use of chemical weapons can depend on the instance and the chain of custody.

"That is what we're investigating now. That's what we're calling on Assad to allow the UN to investigate. This is a very serious matter," Carney said, holding it "essential" to establish a broader process of verification.
Carney, however, made it clear that the US is "not relying on UN alone" and is working with its partners to gather information in this regard.
Reiterating that the use of chemical weapons by the regime would be the responsibility of the Syrian President Bashar al-Assad, he said the US believes, and have assessed, that the chemical weapon stockpiles in Syria continue to be under the control of the Syrian regime led by Assad.

"I don't want to speculate on the incidents that we have assessed with varying degrees of confidence have occurred or may have occurred."
"We are further investigating all credible information about possible use of chemical weapons and call on Assad to comply with his own request for an investigation by allowing that team in to investigate. It's ready to go," he said.