Hassan Nasrallah, leader of the Lebanese militant Shiite Muslim group Hezbollah, has called for his militants to commit to the fight against rebel forces in neighboring Syria. In his most forthright affirmation of Lebanese fighters’ presence in Syria to date, Nasrallah noted during a televised address that an opposition victory in Syria would pose a threat to Lebanese security.

“This battle is ours ... and I promise you victory,” Nasrallah said, according to BBC News. His comments came as rebels battled against Syrian and Lebanese forces outside the strategic Syrian town of Qusair, which is close to the Lebanese border.

At least 94,000 people have died in the Syrian conflict, which began in March 2011 and pits rebel fighters loosely united under the banner of the Free Syrian Army, or FSA, against forces loyal to the regime of President Bashar Assad.

Hezbollah is a close ally of the Assad regime, in part because both entities have ties to Iran -- a Shiite-majority country -- while the Syrian revolutionaries are mostly Sunni Muslims.

Within Lebanon, Shiite and Sunni Muslims have had a volatile relationship for decades: The country is still recovering from a 1975-1990 civil war that exacerbated religious divisions and killed about 120,000 people. Iran is Hezbollah’s main benefactor, but Syria lies between these two allies and has been an important conduit for Iranian funds and weaponry. If the Assad regime is defeated, Hezbollah -- which already has a tense relationship with Israel -- will be surrounded by hostile neighbors.

Hezbollah has grown stronger over the past few years, thanks in large part to hundreds of millions of dollars in funding and tens of thousands of rockets and missiles from Iran, and its militants have been committed to the fight against the FSA and other jihadist elements of the opposition.

Syrian violence has already leaked into Lebanon. On Saturday, the northern economic hub of Tripoli -- home to both Sunnis and Shiites -- was beset by violent clashes between supporters and opponents of the Syrian rebellion. Security sources told Reuters that the conflict there has cost 25 lives over the past week.

Just before Nasrallah’s address Saturday, Syrian regime forces made a renewed push against the rebel forces surrounding Qusair, capturing back much of the territory. Rebels are reportedly still fighting there to maintain control of valuable supply lines that connect them with allies in Lebanon. The Syrian Observatory for Human Rights reported that at least 30 people died in the Qusair clash Saturday.