Nusra Front says U.S.-led air strikes in Syria will fail

Abu Mohamad al-Golani, in an audio message posted on pro-Nusra jihadi forums, urged European and U.S. citizens to denounce the U.S. actions if they wanted to keep out of the war.

"Muslims will not watch while their sons are bombed. Your leaders will not be the only ones who would pay the price of the war. You will pay the heaviest price," he said, warning that the battle would be brought "to the hearts of your homes".

"You should protect yourselves from this war by standing against the decisions of your rulers and stop them from bringing you the woes (of war)," he said.

The United States has been carrying out strikes against Islamic State fighters in Iraq since Aug. 8. It opened a new front on Sept. 23, attacking militants in neighboring Syria.

Washington says the campaign, backed to varying degrees by Arab and Western allies, is aimed at "degrading and destroying" militants who have captured swathes of both Iraq and Syria.

Islamic State and the Nusra Front share the same ideology and rigid Islamic beliefs, but they fell out during a power struggle and have been battling each other this past year.

Nusra Front is now coming under pressure from its own members to reconcile with Islamic State and join forces to fight what they describe as a "crusader" campaign against Islam.

At least 50 fighters from the Nusra Front were killed in the first wave of U.S.-led attacks in Syria last Tuesday, a British-based monitoring group said.

The air assault is also believed to have killed Mohsin al-Fadhli, the leader of another al-Qaeda linked organization, the Khorasan group, which worked in league with the Nusra Front.

Golani did not directly mention Fadhli, but said the air attacks had killed fighters whose "loss would be felt on the whole war, not just on the Front", making clear that they had suffered a significant setback.

However, he predicted that in the end, they would win the war "even if we suffer some pain during it."

He also urged Syrian rebels not to take advantage of the U.S. strikes and hit out at Islamic State, even if they had suffered at the hands of the hardline group.

"(Islamic State injustice) should not push any of you to be driven behind the West and take part in the alliance which they want to use to end jihad." he said.

He also urged Sunni Muslims in neighboring Lebanon to quit the army, which, he said was receiving its orders from Hezbollah -- a Shi'ite militant group that has sent fighters to help Syrian President Bashar al-Assad.