Lebanese Shiite group Hezbollah's decision to fight openly alongside the Syrian regime will increase Lebanon's involvement in Syria's conflict, despite a policy of neutrality, analysts say.
But despite inflaming tensions, the country is unlikely to face serious instability as a result, because none of its political forces have an interest in such a scenario for now, they say.
"Hezbollah's public involvement is no longer the world's worst-kept secret, and now we are in a crisis where the Lebanese are not only politically divided... but also militarily divided," Ghassan al-Azzi, a professor of political science at the Lebanese University, told AFP.
"Hezbollah's involvement in the Syrian crisis now involves all of Lebanon because we've heard from the other side calls to fight jihad alongside the opposition to the Syrian regime," he added, referring to Lebanon's Sunni community.
This week, senior Hezbollah official Nabil Qauq defended the group's actions in Syria, where its elite fighters are reportedly leading the battle in parts of the Qusayr area of central Homs province near the border.
He said the group's members were carrying out "a national and moral duty" to defend Lebanese citizens living in border villages inside Syria.
In response, two Salafist Sunni Lebanese sheikhs urged their followers to go to Syria to fight a jihad (religious war) in defence of Qusayr's Sunni residents.
"There is a religious duty on every Muslim who is able to do so... to enter into Syria in order to defend its people, its mosques and religious shrines, especially in Qusayr and Homs," Sheikh Ahmed al-Assir told his followers.
For now, experts say, such calls on the part of Lebanon's Salafists are largely bluster because the movement is far from able to wield either the arsenal or the fighting forces of Hezbollah.
"Talking without doing anything is less intelligent than doing something without talking about it," Azzi said.
But Wadah Charara, a sociology professor at the Lebanese University, said there was little reason to think the inflamed rhetoric would produce serious domestic instability for Lebanon.
"The impact of the Syrian crisis on Lebanon is worrying, and there may be some incidents, but the general political trend is towards stabilisation and not upheaval," he said.
-- Rising numbers of Hezbollah dead --
Charara, an expert on Hezbollah, said it was forced to publicly acknowledge its role in the conflict by the rising number of deaths among its fighters in Syria.
"It's a 'common sense' policy. In the last year, the party has published photos of some of its activists killed in Syria, but the phenomenon gained momentum with the increasing number of deaths and burials. They couldn't hide it anymore," he said.
The movement began explaining to the Shiite community, its base, that it was acting to defend 13 Lebanese Shiite villages inside Syria, which it said were coming under rebel attack.
In addressing the broader public, the movement is trying to maintain the capital it acquired for its "resistance" to Israel during a devastating 2006 war.
"They explain that their fight against jihadists, who are presented as the 'allies of imperialism and the United States,' is part of a consistent attitude, not a drift," he said.
They say "we maintain the same line by fighting against Israel and against the enemies of the Syrian people," he added.
"But in fact, Hezbollah had no choice," added Azzi, saying the group's loyalty to a regime that has long offered it support and aid forced its hand.
"In any case, it couldn't abandon its alliance with Syria because it's a question of life or death," he added
According to Charara, Hezbollah has around 20,00 fighters, between 5,000 and 7,000 of them battle-hardened forces, and has deployed between 800-1,200 members to fight in Qusayr.