They portrayed the political opposition to Assad as disorganized and hobbled by a lack of experienced leadership. The officials described efforts to unify and attract a broader following among Syria’s minority groups — another objective of U.S. policy — as having limited success. The Syrian National Council, dominated by exiles who are mainly Sunni Muslims, has been trying to attract Christians, Druze and Kurds away from Assad.
Fears that the opposition will oppress minorities or worse have been regularly stoked by the regime, which is dominated by Alawites, an offshoot of Shiite Islam.
The intelligence officials also echoed concerns expressed by U.S. military leaders in congressional testimony this week about providing weapons to the armed elements of the opposition. They are equipped mainly with small arms and rocket-propelled grenades, giving them little firepower compared with Assad’s formidable forces.
An estimated 10,000 to 20,000 soldiers have defected and form the bulk of the Free Syrian Army. It is organized loosely, without effective command and control, and it has few links to the political opposition, according to U.S. intelligence accounts.
Protecting those forces would be a daunting task. One of the officials said that Syria’s air defenses include hundreds of surface-to-air missile sites and thousands of antiaircraft artillery installations.
Describing the dimensions of the challenge, this official said that Syria, barely one-tenth the size of Libya, has an army four times as big with five times the air defense assets, most of it supplied by Russia.
So far, the officials said, the bloodiest attacks against the regime appear to have been carried out by al-Qaeda elements seeking to slip unannounced into opposition groups that do not seem eager to have any affiliation with the terrorist network.
The U.S. officials said that al-Qaeda’s affiliate in Iraq has reversed the flow of a pipeline that once carried fighters and weapons through Syria to battle U.S. forces at the height of the Iraq war.
“That network is still there,” said the first U.S. intelligence official, who acknowledged that the size and composition of the al-Qaeda presence in Syria is unclear. Some al-Qaeda members may be Syrian, others Iraqis.
The officials said their judgment that AQI — as the Iraq affiliate is known — was behind vehicle bombings that killed dozens of people in Damascus and Aleppo in December and January is based more on the nature of the attacks than independent evidence of al-Qaeda involvement.
The greatest damage done so far to Assad’s regime has been economic, intelligence officials said. Sanctions imposed by the United States and the Arab League, as well as European curbs on importation of oil, have caused spikes in unemployment, fuel prices and budget deficits in Damascus.
Over the long term, the officials said, economic hardships may be the most effective tool for unseating Assad. Still, the first U.S. intelligence official said, “to this point, we have not seen that having an effect on the regime’s ability to prosecute the war.”