The toppling of the presidents in Tunisia and Egypt precipitated a tumult of revolutionary fervor that promises to transform the Middle East, but the potential collapse of the Syrian regime could wreak havoc of a very different kind.

In Syria, the fall of President Bashar al-Assad would unleash a cataclysm of chaos, sectarian strife and extremism that spreads far beyond its borders, threatening not only the entrenched rulers already battling to hold at bay a clamor for democratic change but also the entire balance of power in the volatile region, analysts and experts say.

With Syria’s minority Shiite Alawite government overseeing a majority Sunni population, its strategic location and its web of alliances including the radical Hamas and Hezbollah movements, regime change could look a lot more like it did in Iraq than in Egypt — and the ramifications could prove even more profound.

“If the regime collapses you will have civil war and it will spread throughout the region,” engulfing Lebanon, Iraq, Saudi Arabia and beyond, said Hilal Khashan, professor of political science at the American University of Beirut. “A collapse of the Syrian regime is a doomsday scenario for the entire Middle East.”

Many believe that is why the international community, including the United States, has offered such a tempered response to the bloodshed in Syria, the latest Arab country to be swept up in the unrest roiling the region. NATO warplanes are bombing Libya to protect civilians there, but there have been no calls even for Assad to step aside, despite an increasingly violent crackdown by the Syrian military in which at least 550 people have died. On Sunday, hundreds of people were detained as the military swept through towns and villages raiding homes in search of those who participated in recent protests, human rights groups said.

Analyst Rami Khouri describes Syria as the Middle East equivalent of a bank that’s too big to be allowed to fail. “The spillover effect would be too horrible to contemplate,” he wrote in a commentary in Beirut’s Daily Star.

“The specter of sectarian-based chaos within a post-Assad Syria that could spread to other parts of the Middle East is frightening to many people.”

Part of the problem is that so little is known about what would come next should Assad be ousted. Egypt and Tunisia took great leaps into uncertainty when their regimes fell, but in each case the army, a known quantity, asserted its independence and seized power to oversee the transition.

In Syria, the army is so tightly bound to Assad’s Alawite clan that the fall of the regime would almost certainly lead to its disintegration, setting the stage for an Iraq-style implosion in which the state collapses, a majority seeks to exact revenge on a minority and regional powers pile in to assert their own interests, said Joshua Landis of the University of Oklahoma, who writes the blog Syria Comment.

“Syria is the cockpit of the Middle East, and a struggle for control of Syria would be ignited,” he said.

Implications for Iraq

It is the specter of Iraq, where U.S. troops are preparing to withdraw by the end of the year, that most haunts the Obama administration as it seeks to balance demands for a firmer response to the escalating bloodshed with America’s strategic interests, analysts say.

Syria shares a long desert border with Iraq that was for many years the chief transit point for Islamic extremists seeking to join the Sunni insurgency. Only recently, officials say, had the United States noted genuine efforts on the part of the Syrians to curtail the traffic, prompting the United States to return an ambassador to Syria in January for the first time since 2005.

“For the Obama administration, the last thing they want, just at the time they’re withdrawing from Iraq, is a destabilized Syria that would lead to open season for jihadis to cross the border into Iraq,” said David Lesch, professor of Middle East history at Trinity University in Texas.

Iraq’s own Shiite government also views with alarm the upheaval across the border, mindful that the collapse of Syria’s Shiite minority government would almost certainly herald the rise of a Sunni state on its doorstep, and perhaps renewed support for Sunni insurgents still resisting the Shiite ascendancy in Baghdad.

But Iraq is by no means the only country in the region looking askance at the Syrian upheaval. Israel has expressed misgivings about the tumult threatening its chief foe, which has reliably not attempted to recover by force the occupied Golan Heights for nearly four decades — something that could change if a populist Syrian government emerged.

Neighboring Lebanon has its own Sunni-Shiite divide that has long been delineated by pro- and anti-Syrian camps. They have fought one another on many occasions in the recent past, and it is inconceivable that Syria’s troubles would not spill over the border into Lebanon, Khashan said.

To the north, Turkey is concerned about the potential aspirations of Syria’s Kurds, who could seek to assert their identity and claims to statehood as Iraq’s Kurds did after the fall of Saddam Hussein.

Iran has relied on its three-decade-old alliance with Syria to project its influence into the Arab world, and has no wish to see the country controlled by Sunnis. It would almost certainly intervene to support its Alawite allies, just as it intervened in Iraq to help Shiites there. The Obama administration has already accused Iran of helping Damascus repress the revolt.

And the Persian Gulf states, though long on frosty terms with Damascus, also are nervous about the prospect of sectarian conflict, which could leach into Saudi Arabia and Bahrain. For Saudi Arabia, there is also the worry that the assertion of Sunni power in Syria could inspire restive domestic Sunni radicals to intensify their opposition to the monarchy.

Unclear opposition

Yet little is known about who the opposition in Syria is, or who might take over should the regime fall — offering another reason that governments have been so hesitant to call for Assad’s departure.

The authorities have denied entry to the news media, and even before this latest unrest, visas were issued sparingly to journalists and academics, making it hard to know exactly who is behind the sudden, and for many unexpected, outpouring of dissent.

Syria has sought to portray its opponents as armed Islamic extremists intent on sowing sectarian strife, and indeed, the last time there was significant domestic unrest in the country was in 1982, when the Syrian army ruthlessly crushed an insurrection by armed members of the Muslim Brotherhood in the town of Hama, killing between 10,000 and 40,000 people.

Syrian activists bristle at the suggestion that their movement is dominated by Islamists, and say their revolution is no different from the one in Egypt, in which ordinary people spontaneously took to the streets to vent their frustrations with corruption, nepotism and the ruthlessness of the security forces.

“I feel disgusted by how the superpowers make these calculations based on their own interests, while my own people are dying on the streets,” said Mohammed Ali Atassi, a prominent journalist and filmmaker currently in Beirut.

“The Syrians will get their freedom, and we will decide, and the Americans and Europeans will have to accept our choice,” he said. “But in any case, democratically elected governments always go for a peaceful and rational foreign policy.”

‘Overexaggerated’ fears

Some analysts say there is indeed no reason to fear a transition in Syria, which has in any case long been blamed by the West for much of the instability plaguing the region. Predictions of the chaos that would ensue if the regime in Damascus were to fall “are way overexaggerated,” said Riad Kahwaji of the Dubai-based Institute for Gulf and Near East Military Analysis.

Syria has been implicated in the assassination of the former Lebanese prime minister Rafik Hariri, hosts the remnants of Hussein’s Baath Party facilitating the insurgency in Iraq, and enables Iran to ship weapons to Hamas and Hezbollah through its territory. A new regime could prove far more moderate, Kahwaji said.

Yet Syria’s long history as the master manipulator of the Middle East may be another reason that the world is reluctant to alienate Assad. With its long record of sponsoring multiple, shadowy extremist groups in pursuit of foreign policy goals, the Syrian regime is also in a position to unleash considerable chaos across the region should it feel unduly threatened, analysts say.

And that, according to Khashan, the American University of Beirut professor, makes it unlikely the Syrian regime will fall. “Because, to tell the truth, no one wants it to fall, including Israel, the U.S. and the gulf states,” he said.