C.I.A. Said to Aid in Steering Arms to Syrian Rebels WASHINGTON - 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. The clandestine intelligence-gathering effort is the most detailed known instance of the limited American support for the military campaign against the Syrian government. It is also part of Washington's attempt to increase the pressure on President Bashar al-Assad of Syria, who has recently escalated his government's deadly crackdown on civilians and the militias battling his rule. With Russia blocking more aggressive steps against the Assad government, the United States and its allies have instead turned to diplomacy and aiding allied efforts to arm the rebels to force Mr. Assad from power. By helping to vet rebel groups, American intelligence operatives in Turkey hope to learn more about a growing, changing opposition network inside of Syria and to establish new ties. "C.I.A. officers are there and they are trying to make new sources and recruit people," said one Arab intelligence official who is briefed regularly by American counterparts. 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. The administration is also considering whether to help the opposition set up a rudimentary intelligence service. But no decisions have been made on those measures or even more aggressive steps, like sending C.I.A. officers into Syria itself, they said. The struggle inside Syria has the potential to intensify significantly in coming months as powerful new weapons are flowing to both the Syrian government and opposition fighters. President Obama and his top aides are seeking to pressure Russia to curb arms shipments like attack helicopters to Syria, its main ally in the Middle East. "We'd like to see arms sales to the Assad regime come to an end, because we believe they've demonstrated that they will only use their military against their own civilian population," Benjamin J. Rhodes, deputy national security adviser for strategic communications, said after Mr. Obama and his Russian counterpart, Vladimir V. Putin, met in Mexico on Monday. Spokesmen for the White House, State Department and C.I.A. would not comment on any intelligence operations supporting the Syrian rebels, some details of which were reported last week by The Wall Street Journal. Until now, the public face of the administration's Syria policy has largely been diplomacy and humanitarian aid. The State Department said Wednesday that Secretary of State Hillary Rodham Clinton would meet with her Russian counterpart, Sergey V. Lavrov, on the sidelines of a meeting of Asia-Pacific foreign ministers in St. Petersburg, Russia, next Thursday. The private talks are likely to focus, at least in part, on the crisis in Syria. The State Department has authorized $15 million in nonlethal aid, like medical supplies and communications equipment, to civilian opposition groups in Syria. The Pentagon continues to fine-tune a range of military options, after a request from Mr. Obama in early March for such contingency planning. Gen. Martin E. Dempsey, the chairman of the Joint Chiefs of Staff, told senators at that time that the options under review included humanitarian airlifts, aerial surveillance of the Syrian military, and the establishment of a no-fly zone. The military has also drawn up plans for how coalition troops would secure Syria's sizable stockpiles of chemical and biological weapons if an all-out civil war threatened their security. Neil MacFarquhar contributed reporting from Beirut, Lebanon. Souad Mekhennet also contributed reporting.