David Petraeus, the retired general and former CIA director, said the U.S. should consider working with members of an al Qaeda-affiliated group in Syria to fight the so-called Islamic State in Iraq and the Levant terrorist group.

David Petraeus, the retired general and former CIA director, said the U.S. should consider working with members of an al Qaeda-affiliated group in Syria to fight the so-called Islamic State in Iraq and the Levant terrorist group.

In an exclusive statement to CNN, the former head of Central Command who led coalition forces in Iraq and Afghanistan, said some members of the al-Nusra Front in Syria could be convinced to join the coalition against the ISIL.

"We should under no circumstances try to use or co-opt Nusra, an al Qaeda affiliate in Syria, as an organization against ISIL," he told CNN. "But some individual fighters, and perhaps some elements, within Nusra today have undoubtedly joined for opportunistic rather than ideological reasons. They saw Nusra as a strong horse, and they haven't seen a credible alternative, as the moderate opposition has yet to be adequately resourced.

"The question, therefore, is whether it might be possible at some point to peel off so-called 'reconcilable' who would be willing to renounce Nusra and align with the moderate opposition [supported by the U.S. and the coalition] to fight against Nusra, ISIL and Assad," Petraeus added. "Doing so would require both the rise of much stronger, moderate opposition groups — backed, again, by the U.S. and the coalition seeking to defeat ISIL — and at the same time, intensified military pressure on all extremist groups."