(CNN) -- The brazen attack that killed several senior leaders of the Syrian government Wednesday represents a profound psychological blow that could loosen President Bashar al-Assad's grip on power, several experts said.
The blast followed a sharp increase in fighting in Damascus in the past few days and marked the most significant attack on al-Assad's inner circle in 16 months of fighting that government opponents say has killed more than 16,000 people. It killed the country's defense minister, emboldened anti-government rebels and immediately raised questions about the stability of al-Assad's regime.
"How long it can withstand the pressure it is under is an open question, but it seems likely that it will not be able to withstand them indefinitely," said Jeffrey White, a defense fellow for the Washington Institute for Near East Policy think tank and a former member of the U.S. Defense Intelligence Agency. "Things are tilting more and more against the regime."
He said he believes that trend is becoming irreversible.
Stephen Starr, a freelance journalist who spent the past five years in Syria and is author of the book "Revolt in Syria," said the attack signals a new stage in the conflict.
"I think actually we are entering the final stage of the revolution; the regime is probably going to fall," he said.
The attack could prompt more Syrian troops to defect, analysts said. It could also stretch the military thin if al-Assad moves reinforcements to Damascus from other parts of Syria that have been engulfed in conflict.
U.S. Defense Secretary Leon Panetta said Wednesday that the violence in Syria "is rapidly spinning out of control," but several experts warned against overstating the bombing's effect.
Dan Plesch, director of the Centre for International Studies and Diplomacy at the School of Oriental and African Studies in London, warned against seeing the attack as a turning point.
"We shouldn't exaggerate it," he told CNN. "Clearly, it's very serious for the regime, and all the international attention that comes from what in any other environment one would call a terrorist action against the Syrian defense minister and the Defense Ministry."
But, he said, "I think it's too early to talk about the imminent fall of the regime because the army as a whole still seems to be a coherent and large and very heavily armed force."
Jordan's King Abdullah II, one of the first Arab leaders to call for al-Assad to step down, told CNN that he didn't think the attack means the regime is about to crumble.
"This was a tremendous blow to the regime, but again, Damascus has shown its resilience, so I think maybe we need to keep this in perspective," the king said told CNN's Wolf Blitzer. "Although this is a blow, I'm sure the regime will continue to show fortitude, at least in the near future."
Analysts long have said that there could be a turning point in Syria if the unrest that has raged in major provincial cities such as Homs, Hama, Daraa, and Deir Ezzor were to spread to the larger cities of Damascus and Aleppo.
In recent months, attackers have staged high-profile bombings in those cities and battles have raged in Rif Damashq, the province that includes the Damascus suburbs.
White said the latest attack and the fighting in the heart of the capital expose the vulnerability of al-Assad's regime.
"It's in the regime's backyard," he said. "The people who run the place can see it or hear it."
White said the armed opposition has grown in power and includes growing numbers of defectors and civilians called the Free Syrian Army as well as jihadist groups.
A focus on Damascus could weaken Syria's security push in the other cities besieged by al-Assad's soldiers and militia allies, White said.
"If they can't bring the thing under control in Damascus, then they will probably bring in reinforcements outside of Damascus," he said.
He noted that the military "has withstood the stresses of a year of combat against an increasingly capable opponent, the steady expansion of its task, and a running wound in the form of defections and casualties."
White said the Russian and Iranian governments, longtime friends and allies to al-Assad, are constantly assessing the situation. Russia will try to avoid being "caught on the wrong side" and Iran "will never come out against the regime," but it may back away from al-Assad, he said.
Rime Allaf, an associate fellow at the Chatham House think tank, supported theories that the attack was the work of an insider: "Someone who has the full trust of the upper echelons of the regime and over a period of time gathered all these explosives until this bomb was detonated," she said.
The attack could signal a rift in the regime, with people in top posts who disagree with al-Assad "taking matters into their own hands."
"That means that they don't know any more at the very top who they can trust," she said, "and they understand that this means it's much more widespread than they initially thought, this opposition to them."
The attack reflects on sectarian issues as well. The defense minister was Christian in a regime dominated by Alawites, an offshoot of Shiite Islam.
The regime "has been using the sectarian line, but the opposition and the rebels have increasingly repeated that they do not view it in those terms," she said. "So it's not the Alawites who are crumbling, it's a regime. ... It means many people within that regime, whatever religious denomination they are, they don't necessarily agree with the way things are happening."
Aram Nerguizian, a Syria expert at the Center for Strategic and International Studies in Washington, said many Syrians, both loyalists and those who are on the fence, might not approve of "tactics that give great cause (for concern about) any future stability in Syria."
Al-Assad will likely bolster the security response, based on the regime's counterterrorism rhetoric.
Nerguizian said it's too soon to say whether the attack and the offensive in Damascus represent turning points. That offensive, he says, "has yet to make definitive gains so far."
Plesch told CNN he does not consider the conflict to be a civil war because the anti-government uprising includes international involvement.
Opposition forces are being "quite well armed and probably trained by external clandestine forces from the Gulf states and probably from Turkey," he said.
Anthony Skinner, a Middle East expert at the Britain-based Maplecroft risk-analysis firm, told CNN the latest events represent a "massive psychological blow for the regime" that will hasten al-Assad's demise.
But he said that, while the Free Syrian Army has a presence in Damascus, it remains outmanned and outgunned.
It doesn't have a strong command and suffers from supply-line challenges, making it hard to deliver armaments to its forces, he said. It also lacks the heavy weaponry that would allow it to enter into prolonged face-to-face confrontations with regime forces.
Elements within the regime want to jump ship from a "sinking vessel" and join the opposition, but they have been held back by the threat that their family members would be arrested and tortured or killed, Skinner said.
"Bashar al-Assad does still have a fairly cohesive elite of predominantly Alawite politicians and security personnel around him," Skinner said "We do envisage senior regime members still wanting to fight to the end because there is no escape route for them, effectively."
The international community, Russia and China aside, has not been able to devise a solution, Skinner said. "Armed intervention is clearly not in the cards ... so this has been a major source of frustration."
But he said that, if "this overall dynamic continues, then I think you would ask any Syrian and their assessment of Bashar al-Assad's prospects would be very negative. It doesn't appear likely that he will be able to hang on, whether that's in the medium term, or in long term or even, some people are wondering if that's possible in the short term."