Since the beginning of the year, according to four American and Middle Eastern officials with knowledge of intelligence reports on the weapons, Qatar has used a shadowy arms network to move at least two shipments of shoulder-fired missiles, one of them a batch of Chinese-made FN-6s, to Syrian rebels who have used them against Mr. Assad’s air force. Deployment of the missiles comes at a time when American officials expect that President Obama’s decision to begin a limited effort to arm the Syrian rebels might be interpreted by Qatar, along with other Arab countries supporting the rebels, as a green light to drastically expand arms shipments.
