The Al-Qaeda-linked Islamic State of Iraq and the Levant has reached out to other rebel groups in Syria to head off infighting, in an audio message posted online Sunday.
"Today, the (Islamic) state is reaching out to you to stop fighting us, to focus on fighting the nusairiyah," the voice in the message, purportedly that of ISIL chief Abu Bakr al-Baghdadi, said, using the term often used by jihadists to refer to the Syrian regime.
The remarks mark a shift for ISIL, which said earlier this month it would "crush" opposition fighters and considered members of the Syrian National Coalition and the military command of the Free Syrian Army to be "legitimate targets".
Baghdadi, in the audio message posted on jihadist forums, accused rebel groups of "betrayal".
"Anyone who fought against us should review his stance," he said.
"You have stabbed us in the back, as all of our soldiers were on the frontline."
He continued, referring to various parts of Syria: "We used to have an army who implemented a plan to invade Aleppo and advance to the western front, and we used to have forces in Hama and we used to have forces in Idlib.
"But all of this has stopped in one night because of the betrayal."
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Baghdadi urged his group's fighters to "not betray anybody", and recommended they "forgive" other rebels.
"Forgive them, to concentrate on your enemy, who is the enemy of the Sunni people."
Most rebels in Syria are Sunni Arab, and have fought against the regime of Syrian President Bashar al-Assad, whose Alawite sect is an offshoot of Shiite Islam.
But ISIL has faced a rebel backlash in Syria and has been hit by days of fighting against a coalition of moderate and Islamist rebels, including with Al-Nusra Front, Al-Qaeda's official affiliate in Syria.
Baghdadi had sought to merge his group with Nusra, but they rejected the alliance and pledged allegiance directly to Al-Qaeda chief Ayman al-Zawahiri.
Since then, the two groups have functioned separately, though Nusra has remained largely neutral in the latest infighting, and the group's leader has called for an end to the clashes, warning it would benefit the regime.
But ISIL spokesman Abu Mohammed al-Adnani sounded a defiant tone in his own audio message earlier in January, calling for ISIL forces to "crush them (the rebels) totally and kill the conspiracy at birth."
In the latest audio message, Baghdadi also issued a warning to Washington, going on to say, "Beware America ... that the proxy war will not protect you in Syria, and soon you will be forced into direct confrontation."
"The sons of Islam are getting themselves ready for that day."