The US and its allies have “no smoking gun” proving Syrian President Bashar Al-Assad personally ordered his forces to use chemical weapons to attack a rebel-held Damascus neighbourhood, US national security officials said yesterday.

In secret intelligence assessments and a still-unreleased report summarising US intelligence on the alleged gas attack on August 21, US agencies express high confidence that Syrian government forces carried out the attack, and that Assad’s government therefore bears responsibility, the officials said.

“This was not a rogue operation,” one US official said.

However, the evidence does not prove that Assad himself ordered that chemical munitions be used, according to the officials, who spoke on condition of anonymity.

Evidence that forces loyal to Assad were responsible goes beyond the circumstantial to include electronic intercepts and some tentative scientific samples from the neighbourhood which was attacked, officials said.

While Obama has not yet announced a decision on military action, he has left little doubt the choice was not whether but when to punish Assad’s government for the attack, in which hundreds of people died.

During the week, US government spokespeople have made increasingly emphatic statements declaring that chemical weapons were used and that Assad’s government, rather than rebel forces, were responsible for using them.

“This was a massive, large-scale... multiple-faceted attack against a wide swath of area using very sophisticated rockets, very sophisticated delivery systems that were armed with chemical weapons. There is one party in Syria who has the capability to do that, and it’s the Assad regime,” State Department spokeswoman Marie Harf has said.

Harf added that US officials “ultimately, of course, hold President Assad responsible for the use of chemical weapons by his regime against his own people, regardless of where the command and control lies.”

US security sources and sources close to allied governments say evidence suggests that the initial decision to use chemical weapons may have been made by a field commander rather than in an order from the highest level of the Syrian government. US intelligence stated that they did intercept communications discussing the attack between officials in cen-tral command and in the field. But these do not clearly implicate Assad or his entourage in ordering the use of chemicals, sources familiar with the material said.

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