But the use of such weapons would be unlikely to usher in the sort of game-changer that would bring about the downfall of the regime, and a new political order for Syria.

"I don't think the mere presence of shoulder fired missiles is going to lead the people who are fighting for Bashar al-Assad to stop fighting for Bashar al-Assad," Ford said.

But a U.S. official told CNN the "armed opposition is maturing" and having an impact on the regime.

"It's making important tactical gains that could eventually trigger a strategic shift in the conflict," the official said. "They haven't reached that point yet, but the span of regime control is narrowing, and Assad's forces are having greater difficulty beating back the insurgents' progress."

Ford is still operating as the U.S. envoy to Syria from his office in Washington. He left his post in Damascus last February when the United States closed its embassy due to the deteriorating security situation.