For the last week or so, Syria has been moving heavily armed elite military units to the Lebanese border - with up to 25,000 massed there by early last week. Backed by tanks, armored vehicles and attack helicopters, the units were on "maximum war footing," eyewitnesses say.

Damascus says the build-up is a response to smuggling rings that run the black market in the Syrian capital and major provincial centers. My Lebanese contacts call that explanation "laughable" - noting that Syrian elite itself runs the black market in both countries through the security services.

The buildup covers only the northern portion of the Syria-Lebanon border, leaving the eastern portions in the hands of the Iran-financed (and thus Syria-allied) Hezbollah militia.

And Lebanese analysts say the type of force Syria is massing is better suited for a classical invasion than for chasing small and scattered groups of bandits along the border.

More ominously, the official Syrian media claim that the force could be used to "hunt down and eliminate fundamentalist terrorists linked to al Qaeda." This refers to a group called Fatah al-Islam (Conquest of Islam), which fought the Lebanese army in the northern city of Tripoli, close to the Syrian border, for months before being flushed out. Since then, the group has gone underground; it is suspected in a number of assassinations and suicide attacks.

In his meetings with French President Nicolas Sarkozy and Turkish Prime Minister Recep Tayyib Erdogan last month, Syrian President Bashar al-Assad promised, without going into details, that he'd "play a more active part" in the War on Terror. The Lebanese see Syria's claimed intent to fight al Qaeda-linked terrorists as a ploy to "hoodwink the Americans."

"They want to present their invasion as part of the global War on Terror led by the United States," says a Lebanese analyst.

Indeed, evidence suggests that Syria assisted the emergence of Fatah al-Islam in the Tripoli area. Lebanon borders only two other nations, Israel and Syria. Since it's unlikely that Fatah al-Islam killers entered Lebanon from Israel, the assumption that they came through Syria can't be dismissed easily.

Plus, shortly after Fatah al-Islam seized control of the Nahr al-Bared area close to Tripoli, a pro-Syrian Palestinian group, Fatah al-Intifada (Conquest of the Uprising), merged with it. That couldn't have happened without Damascus' approval.

Fatah al-Islam members captured by the Lebanese army have said that almost all the group's fighters came from other Arab countries. Once installed in Tripoli, they linked up with "sleeper" Palestinian terror networks there and launched a joint bid for the control of the mostly Sunni city.

Yet another pretext the Syrians invoke for a possible intervention in Lebanon is the protection of the Alawite religious minority.

The Alawites, an esoteric sect most Muslims regard as heretics, number some 50,000 around Tripoli. But they account for 11 percent of Syria's population and dominate its government and armed forces through the Assad dynasty.

In its brief domination of Tripoli, the Fatah al-Islam gang refrained from attacking Alawite neighborhoods, giving credence to claims that it was a Syrian proxy.

When Syria invaded and occupied Lebanon in the 1970s, its excuse was that it wanted to protect the Christian minority against the Palestinians and their allies. Today, with a majority of Lebanese Christians opposed to Syrian intervention, it is painting the Alawites as those needing protection.

One thing is certain: The Syrian buildup has little, if anything, to do with fighting smugglers or terrorists. Syria has special police and security units for such tasks.

President Assad might well be tempted to remedy his humiliation in 2005, when he was forced to withdraw his army from Lebanon after 29 years of occupation.

If so, he may well be eyeing a brief window of opportunity right now. America is preoccupied by the financial crisis and the presidential campaign. And Europe, led by Sarkozy, has just committed itself to rehabilitating Syria and doesn't want to jeopardize the supposed gains of its "positive dialogue" with Damascus.

Turkey would be in no position to criticize a Syrian incursion into Lebanon - Turkish forces have repeatedly entered Iraq, ostensibly to hunt down Kurdish rebels. And Russia - grateful for Syria's support in the recent war with Georgia - wouldn't frown at a Syrian move to topple the pro-Western regime in Beirut. Israel, politically paralyzed and possibly heading for early elections, is in no position to oppose a Syrian invasion.

So far, Syria's military gesticulations on the Lebanese border haven't elicited warnings from the United States or the European Union, encouraging the hard-line faction in Damascus that is pressing for a "return to Lebanon."