SIDON, Lebanon – On a main road connecting the Lebanese capital with the south, Sheik Ahmad Assir kneels under a blazing sun to pray and then sits down with supporters at his anti-Hezbollah protest camp and launches into a new tirade against Lebanon´s most powerful and well- armed force.

"By God, Nasrallah, I will not let you sleep at night," he vows in a fiery speech, addressing Hezbollah´s leader, Sheik Hassan Nasrallah.

Few in Lebanon have dared take on the Shiite militant group in such a public way, but Assir, a hardline Sunni cleric, senses weakness. He sees a chance to push back against Hezbollah´s domination of the country´s politics.

The growing popularity among some Sunnis of the previously little known local cleric is a sign of how vulnerable Hezbollah has become as it faces the possibility of the downfall of its crucial ally, President Bashar Assad in Syria. Its reputation as a popular resistance movement has already taken a severe beating for siding with Syria against the anti-Assad uprising even after it supported Arab revolts in Egypt, Tunisia, Libya and Bahrain.

"This is the start of what will become Lebanon´s Tahrir Square," Assir, wearing a long robe and white skullcap, told The Associated Press at his protest site, where some 150 Sunni conservative supporters have been camped out for some three weeks. "They have humiliated us for long enough. It´s about our dignity now. I can´t live like this, it´s enough."

"May you triumph over the Party of the Devil!" came a shout of support to Assir from one bearded protester, who traveled from the northern, Sunni-dominated city of Tripoli to join in. He used a play on Hezbollah´s name, Arabic for Party of God.

Assad´s fall would be a nightmare scenario for Hezbollah. Any Sunni- led new regime would likely be far less friendly to the group, or even outright hostile. Regime change in Syria could heavily damage its ally´s political clout in Lebanon and knock out a third of the "Iran-Syria-Hezbollah" axis of "resistance" to Israel.

Iran remains Hezbollah´s most important patron, but Syria is a crucial supply route. Without it, Hezbollah will struggle to get money and weapons as easily.

Nasrallah admitted how crucial the alliance with Damascus is in a speech Wednesday night after Assad´s regime suffered its hardest blow yet in the conflict — a bomb blast that killed three major regime figures, including the defense minister and Assad´s brother-in-law.

Nasrallah called the Syrian regime a "bridge" and a "critical support" for Hezbollah´s "resistance" against Israel.

"The most important weapons with which we fought Israel in the July war came from Syria," he said, in reference to Hezbollah´s monthlong 2006 war with Israel.

In the face of the Syria crisis, Hezbollah is treading carefully to retain the power it has built up over the past 30 years in Lebanon, a deeply divided country where its strength is resented by Sunnis and some in the Christian community.

The group´s main strategy for doing so appears to be to lay low and avoid aggravating the volatile fault line between the Sunni and Shiite communities, which each make up about a third of Lebanon´s population of 4 million.

Lebanon´s sectarian tensions have already been worsened by the crisis in Syria, where the overwhelmingly Sunni opposition is struggling to oust a regime dominated by Alawites, an offshoot of Shiite Islam.

Regional shifts also weigh on Hezbollah. The so-called Arab Spring sweeping the Middle East has so far led to the rise of conservative Sunni Islamists deeply resentful of Shiite powerhouse Iran and its allies Syria and Hezbollah.

"Hezbollah has accepted that this is going to be a protracted crisis in Syria and by virtue of that, the group has been much readier to calibrate and reduce its footprint," said Aram Nerguizian, a visiting fellow at the Center for Strategic and International Studies in Washington.

Over the course of Syria´s 16-month-old uprising, he and other analysts have noted a subtle shift in Hezbollah´s public position. Early on, Nasrallah embraced Assad, casting him as a reformer in speeches that infuriated Syrian protesters. He has since then somewhat modified his stance, calling on both sides to cease the violence and engage in dialogue.

Assir´s rapid rise and growing following are symptoms of the deep frustration among Lebanon´s Sunnis who resent the Hezbollah-led Shiite ascendancy to power in Lebanon.

The 44-year-old, bespectacled, skinny cleric with a long bushy beard was previously little known, a preacher at the Bilal Bin Rabah Mosque in Sidon. Now he is openly challenging and taunting Hezbollah like few have dared before, even taking aim at Nasrallah, a revered figure usually considered a red line in Lebanon.

Assir calls his protest camp an "uprising" against Hezbollah´s weapons, aimed at bringing the powerful arsenal of the group´s guerrilla force under the control of the government. Hezbollah, the country´s strongest armed force, has resisted pressure to do so for years.

Assir set up the camp blocking a main road in the southern coastal city of Sidon. The city is the gateway to Hezbollah´s traditional stronghold in the south and links the group´s command center in Beirut´s southern suburbs with front line villages in the south.

Sunni bitterness still runs deep over clashes in May 2008, when Hezbollah gunmen swept through Sunni neighborhoods in Beirut after the pro-Western government of that time tried to dismantle the group´s crucial telecommunications network. More than 80 people were killed in those clashes.

Moreover, a U.N.-backed special tribunal has accused four Hezbollah members in the 2005 assassination of former Prime Minister Rafik Hariri, Lebanon´s most powerful Sunni leader. Hezbollah says the tribunal is a tool of Israel and the West.

Hezbollah still is Lebanon´s single most influential player with considerable support among Shiites and unprecedented political clout. It holds a dominant role in Beirut´s government and the prime minister is an ally, after the fall of the previous government sidelined Hezbollah´s opponents, the U.S.- and Western-backed factions led by Hariri´s son Saad. As a result, its extensive arsenal of weapons and rockets is virtually untouchable for the moment.

Hezbollah has not directly commented on Assir´s tirades and has gone into great lengths to rein in members who might clash with his supporters.

Their reaction has also been muted to the abduction of 11 Shiite pilgrims in May by rebels in Syria who demanded Nasrallah apologize for pro-Assad comments. The kidnapping is seen as an attempt to draw Hezbollah retaliation,

"Hezbollah knows it´s absolutely not in its interest to have a civil war in Lebanon," said political analyst Abdelwahab Badrakhan, writing in the Lebanese daily An-Nahar. Hezbollah and Iran´s main goal is to preserve the political cover to ensure the group´s hold on its weapons and freedom to operate.

Nerguizian said a new conflict in Lebanon could erupt if Hezbollah doesn´t agree to a new formula to share power with its rivals. "The Shiites have to deal with the reality of what happens to a minority group when it takes on too much and doesn´t share enough," he said.

At the camp in Sidon, Assir has a hero status among the protesters.

Maysa Sabbagh — a 27-year-old who like other women at the camp was covered from head to toe in black, only a small slit revealing her brown eyes — said she was once an admirer of Hezbollah for its fight against Israel but grew disillusioned when the party when it turned its guns on other Lebanese in 2008.

"Sheik Assir is speaking for all of us," she said, a Blackberry in her hand and an iPad perched on her lap. Assir "says what others do not dare say." (© 2012 The Associated Press 07/19/12)