BEIRUT — The leader of al-Qaida’s Syria affiliate vowed Sunday that his group would “use all possible means” to fight back against airstrikes by the U.S.-led coalition and warned that the conflict would reach Western countries joining the alliance.

The U.S. views the affiliate, known as the Nusra Front, as a terrorist group, but Syrian rebels have long seen it as a potent ally against both the Islamic State extremist group – which is the main target of the coalition – and Syrian President Bashar Assad’s forces.

Syrian rebels, activists and analysts have warned that targeting the Nusra Front will inject more chaos into the Syrian conflict and indirectly help Assad by striking one of his main adversaries. The U.S. insists it wants Assad to step down, but is not targeting his forces, which are best placed to benefit from the airstrikes.

In a 25-minute audio recording, Nusra Front leader Abu Mohammed al-Golani portrayed the U.S.-led coalition as a “Crusader alliance” against Sunni Muslims and vowed to fight back.

“We will use all that we have to defend the people of Syria…from the Crusader alliance,” al-Golani said. “And we will use all possible means to achieve this end,” he said.

He warned Western countries against taking part in the alliance in words that echoed those of the late founder of al-Qaida, Osama bin Laden.