A small number of C.I.A. officers are operating secretly in southern Turkey, helping allies decide which Syrian opposition fighters across the border will receive arms to fight the Syrian government, according to American officials and Arab intelligence officers.

The weapons, including automatic rifles, rocket-propelled grenades, ammunition and some antitank weapons, are being funneled mostly across the Turkish border by way of a shadowy network of intermediaries including Syria’s Muslim Brotherhood and paid for by Turkey, Saudi Arabia and Qatar, the officials said.

The C.I.A. officers have been in southern Turkey for several weeks, in part to help keep weapons out of the hands of fighters allied with Al Qaeda or other terrorist groups, one senior American official said. The Obama administration has said it is not providing arms to the rebels, but it has also acknowledged that Syria’s neighbors would do so…

American officials and retired C.I.A. officials said the administration was also weighing additional assistance to rebels, like providing satellite imagery and other detailed intelligence on Syrian troop locations and movements.