CIA deputy director Michael Morell gave the assessment in an interview published by the Wall Street Journal as he prepares to retire after 33 years with the agency.
Mr Morell said there were more foreign fighters flowing into Syria each month to take up arms with al-Qaeda-affiliated groups than there were going to Iraq to fight with al-Qaeda at the height of the war there.
The Syrian government's weapons ''are going to be up for grabs and up for sale'' as they were in Libya when Muammar Gaddafi fell, he added.
Read more: CIA warns of crisis as al-Qaeda prepares to pounce
Mr Morell said there were more foreign fighters flowing into Syria each month to take up arms with al-Qaeda-affiliated groups than there were going to Iraq to fight with al-Qaeda at the height of the war there.
The Syrian government's weapons ''are going to be up for grabs and up for sale'' as they were in Libya when Muammar Gaddafi fell, he added.
Read more: CIA warns of crisis as al-Qaeda prepares to pounce