The leader of Lebanon’s Hezbollah admitted for the first time Saturday that his Shiite terrorist group had deployed fighters to Syria, saying his group would not stand idly by while its chief ally is under attack.

In a televised speech commemorating Resistance and Liberation Day, which marks Israel’s 2000 withdrawal from southern Lebanon, Sheikh Hassan Nasrallah said Hezbollah members are fighting in Syria against Islamic extremists who pose a danger to Lebanon.

Nasrallah’s comments Saturday marked the first time he has publicly confirmed his men were fighting in the Syrian civil war. They are also his first statement since Hezbollah fighters have become deeply involved in the battle for the strategically critical Syrian town of Qusair.

He said tens of thousands of Islamic extremists from all over the world have been sent to Syria to fight the regime, but Hezbollah sends “a few” fighters and it is accused of intervening in the conflict.

Defending his decision to send troops to Syria in support of President Bashar Assad’s regime, Nasrallah said that ”Syria is the back of the resistance, and the resistance cannot stand, arms folded, while its back is broken.”

The Shiite leader accused the United States of planning to invade Syria, and of backing takfiris – radical Sunni Islamist groups like Jabhat al-Nusra, which he claimed constituted the majority of the Syrian opposition. Takfiri refers to an ideology that urges Sunni Muslims to kill anyone they consider an infidel.

At the same time, Nasrallah attempted to assuage fears that Hezbollah’s intervention in the Syrian civil war against Sunni rebel groups was driven by sectarian motives.

“We are not evaluating the matter from a Sunni or Shiite perspective, but from a perspective joining all Muslims and Christians together because they are all threatened by this takfiri project that is financed by the US,” he said.

Nasrallah warned his followers that the Assad regime’s downfall would have disastrous consequences for the region. “If Syria [falls] into the hands of America, Israel and the takfiris, the future of Lebanon, Syria, Palestine and the whole region would be dark,” Hezbollah’s al-Manar news site quoted Nasrallah saying.

“If Syria falls, the Palestinian cause will be lost,” he said.

Igniting fears of Israel’s military presence in Lebanon, which ceased 13 years ago to the day, Nasrallah also claimed that Israel would invade Lebanon should Syria fall to American and radical Islamist forces.

Nasrallah told his followers that in the divisive civil war in neighboring Syria, “You can be with whoever side you want… but Hezbollah can be neither with the American side nor with the side of murderers who dig [up] grave or rip [open] chests,” referring to a grotesque video in which a Syrian rebel appeared to eat the internal organs of a dead soldier.

Syria, along with Iran, has been the main backer of Hezbollah and much of the group’s arsenal consisting tens of thousands of rockets is believed to have come through or from Syria.

More than 70,000 people have been killed and several million displaced since the uprising against Assad erupted in March 2011 and escalated into a civil war. The Syrian government and Hezbollah deny there is an uprising in Syria, portraying the war as a foreign-backed conspiracy driven by Israel, the US and its Gulf Arab allies.