Jihadis make certain a messy endgame in Syria

(CBS News) Syrian rebels on Sunday night ramped up their assaults on Damascus, the capital, and Aleppo, the country's largest city.

The U.N.'s peace envoy met with U.S. and Russian diplomats in Moscow again, trying to broker a ceasefire, and there's growing concern over al Qaeda's influence in the rebel ranks.

Video said to show the aftermath of a Syrian air strike provides graphic evidence of a life and death battle which high level diplomats say "is bad and getting worse."

Despite its air power, the Assad regime appears increasingly on the defensive against rebel forces which, according to Israel's ambassador to the U.S., Michael Oren, include a growing number of radical Islamists.

"The jihadi presence is big and getting bigger and the longer the conflict goes on there the bigger it will get," Oren said.

The jihadis are an offshoot of al Qaeda in Iraq, which once fought a no-holds-barred battle against American troops. According to Jeffrey White, a former analyst for the Defense Intelligence Agency, they are now turning the tide against the Assad regime.

"They are very good fighters. They give the rebels a combat edge. They're quite willing to die. They fight on all the key fronts. They're involved in many of the key actions, many of the successful actions of the rebels. These are not people that we want to win," White said.

With the rebels making inroads on Damascus itself, monitoring of Syrian bases where chemical weapons are stored has detected evidence the Assad regime may be preparing to use them in a last-ditch attempt to save itself, an act the Obama administration has warned could trigger military intervention. Worst case scenarios are threatening to become reality.

"It's not going to be a clean outcome in the best of circumstances and now it will be chaotic and messy," White said.

The U.S. has been helping to organize the opposition's military command and later this week is expected to officially recognize its political leadership. What impact that will have on the outcome of the civil war remains to be seen.