“The bulk of evidence proving the Assad regime’s deployment of chemical weapons – which would provide legal grounds essential to justify any western military action – has been provided by Israeli military intelligence. The 8200 unit of the Israeli Defence Forces, which specialises in electronic surveillance, intercepted a conversation between Syrian officials regarding the use of chemical weapons, an unnamed former Mossad official told Focus. The content of the conversation was relayed to the US, the ex-official said. Israel and the US had a ‘close and co-operative relationship in the intelligence field’, he added, but declined to comment specifically on the Focus report.”
http://www.theguardian.com/world/2013/aug/28/israeli-intelligence-intercepted-syria-chemical-talk