The opposition has been saying that the recent spate of bombings in Damascus and Aleppo could be pinned on President Assad who they say was trying to discredit their movement to oust him.

Instead, the US government says that, at least in a couple of cases, Assad is right; al-Qaeda is behind the terror attacks.

McClatchy:

The international terrorist network's presence in Syria also raises the possibility that Islamic extremists will try to hijack the uprising, which would seriously complicate efforts by the United States and its European and Arab partners to force Assad's regime from power. On Friday, President Barack Obama repeated his call for Assad to step down, accusing his forces of "outrageous bloodshed."

The U.S. intelligence reports indicate that the bombings came on the orders of Ayman al Zawahiri, the Egyptian extremist who assumed leadership of al Qaida's Pakistan-based central command after the May 2011 death of Osama bin Laden. They suggest that Zawahiri still wields considerable influence over the network's affiliates despite the losses the Pakistan-based core group has suffered from missile-firing CIA drones and other intensified U.S. counterterrorism operations.

U.S. officials said that al Qaida in Iraq, or AQI, began pushing to become involved in Syria as Assad's security forces and gangs of loyalist thugs launched a vicious crackdown on opposition demonstrations, igniting large-scale bloodshed. Growing numbers of lightly armed army deserters and civilians have joined an armed insurrection, and perhaps thousands of people have been killed.

Zawahiri finally authorized AQI to begin operations in Syria, the officials said, in what's believed to be the first time that the branch has operated outside of Iraq.

From AQ's point of view, it makes sense. As in Mubarak's Egypt, the Islamists had been beaten down by Assad over the years with the Muslim Brotherhood very weak and fundamentalist political parties squelched. Now that Assad is under attack, the religious extremists in Syria are beginning to emerge as a force. And al-Qaeda is seeking to take advantage of the chaos to establish a toe hold in Syria.

One more argument not to arm the Syrian rebels.