LONDON, Aug 29 (Reuters) - The following are excerpts of an assessment by the British government's Joint Intelligence Committee of a suspected chemical weapons attack in Syria last week.

The assessment was supplied by the British government and can be found at

https://www.gov.uk/government/publications/syria-reported-chemical-weapons-use-joint-intelligence-committee-letter

Joint Intelligence Committee assessment:

"A chemical attack occurred in Damascus on the morning of 21 August, resulting in at least 350 fatalities. It is not possible for the opposition to have carried out a chemical weapons attack on this scale. The regime has used chemical weapons on a smaller scale on at least 14 occasions in the past. There is some intelligence to suggest regime culpability in this attack. These factors make it highly likely that the Syrian regime was responsible.

"Extensive video footage attributed to the attack in eastern Damascus (which we assess would be very difficult to falsify) is consistent with the use of a nerve agent, such as sarin, and is not consistent with the use of blister or riot control agents.

"There is no obvious political or military trigger for regime use of chemical weapons on an apparently larger scale now, particularly given the current presence in Syria of the UN investigation team. Permission to authorise chemical weapons has probably been delegated by President Assad to senior regime commanders, such as, but any deliberate change in the scale and nature of use would require his authorisation.

"There is no credible evidence that any opposition group has used chemical weapons. A number continue to seek a chemical weapons capability, but none currently has the capability to conduct a chemical weapons attack on this scale."

Letter from Chairman of Joint Intelligence Committee, Jon Day, to Prime Minister David Cameron:

"It is being claimed, including by the regime, that the attacks were either faked or undertaken by the Syrian Armed Opposition. We have tested this assertion using a wide range of intelligence and open sources, and invited HMG (Her Majesty's Government) and outside experts to help us establish whether such a thing is possible. There is no credible intelligence or other evidence to substantiate the claims or the possession of chemical weapons) by the opposition. The Joint Intelligence Committee has therefore concluded that there are no plausible alternative scenarios to regime responsibility.

"We also have a limited but growing body of intelligence which supports the judgement that the regime was responsible for the attacks and that they were conducted to help clear the Opposition from strategic parts of Damascus. Some of this intelligence is highly sensitive but you have had access to it all.

"Against that background, the Joint Intelligence Committee concluded that it is highly likely that the regime was responsible for the chemical weapons attacks on 21 August. The Joint Intelligence Committee had high confidence in all of its assessments except in relation to the regime's precise motivation for carrying out an attack of this scale at this time." (Reporting by Andrew Osborn and William James; Editing by Guy Faulconbridge/Mark Heinrich)

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