With the opposition fragmented, the West fears that weapons could fall into the wrong hands, notably al Qaeda-backed militants and the Islamist Nusra Front, and wants "guarantees" from opposition fighters before providing the arms.
With cast iron guarantees unlikely and time running out, the way Francehas developed its networks in Syria since the uprising started more than two years ago offers an idea of how Western powers may assess future military help.
"It's not possible to say that we can be 100 percent sure about where the weapons go," said a Western diplomat. "But the risks of porosity are less than the risks of doing nothing."