"From an intelligence point of view the regime has to decide: fight or flight," the senior official said.
Another senior official from the Middle East region underscored that assessment, telling CNN the attacks indicate "strong cracks in the regime."
"This is a potential tipping point," the Middle East official said.
The nature of the violence and the proximity to al-Assad's inner circle of power is causing the increased concern from American government officials in the last few days, the American source said. A second senior U.S. official concurred with that assessment.
When asked if the al-Assad regime also believes itself to be at a decision point, the U.S. official the there is at least some information to back up that belief.
But the king of Jordan, whose country borders Syria, warned that despite a "tremendous blow," the regime is not going to give up.
"Damascus has shown its resilience. So I think maybe we need to keep this in perspective, although this is a blow," King Abdullah II said in an interview that aired Wednesday on CNN's Situation Room with Wolf Blitzer. "I'm sure that the regime will continue to show fortitude, at least in the near future.
"I don't think we should jump to any conclusions of writing the regime off in the near future."
When Defense Secretary Leon Panetta told reporters Wednesday that the Syrian situation is "rapidly spinning out of control," he was reflecting growing concern about the fighting having reaching the Syrian capital and growing worries about Syria's chemical weapons, officials tell CNN.
With the Syrian regime now having moved some of its chemical weapons on at least one recent occasion, the Obama administration is stepping up efforts to conduct an "assessment of intentions" of the Syrian regime to employ that deadly arsenal against its own people, according to the second senior U.S. official who has direct knowledge of the efforts.
At the same time, senior U.S. officials involved in this issue have spoken privately but directly with their Russian counterparts in the past several days to reinforce that any use of the chemical weapons by the Syrians is a so-called "red-line" for the United States.
"This would be a game changer," the official said, who declined to be identified because the sensitivity of the information.
The official emphasized that the U.S. has been watching Syria's chemical and biological weapons sites for months to determine the security of the weapons. But since Assad moved some from a facility recently, the challenge has been to figure out what, if anything, the Syrian leader plans to do with them, he said. "The movement of the chemical weapons has generated additional concern inside the U.S. government."
At a Pentagon press conference, the chief UK defense minister made it clear that both the United States and Britain want to see Russia and China weigh in.
"The regime exists at the moment because it receives tacit support from other powers in the world," said UK Secretary of State for Defense Phillip Hammond. "If those powers are sending clear messages about the limits of their tolerance for the activities of the regime, that will be an effective constraint on the activities of the regime. So our diplomacy has to focus on getting those who have the greatest influence with the regime to ensure that it acts responsibly in relation to chemical weapons."
One challenge is to define inside the Obama administration the specific terms of what the red line may be. Officials have suggested it's the "employment" of weapons that is the red line, but acknowledged at that point it may be too late to stop their actual use. The U.S. is making the case to the Russian that they must once again make clear to al-Assad the implications of using chemical weapons.
"It's our sense even though the Russians are supporting the Assad regime that chemical weapons are a significant concern to them," the official said. "They understand the stakes get much higher and their moral ground gets much lower" if chemical weapons are used.
The Jordanian king also voiced concern about any scenario involving chemical weapons.
"I think at the end of the day, all of us would suffer from that. I'm sure that (the Russians) would be very supportive of international reactions, because at the end of the day, we all pay the price," Abdullah said.