Most likely with the newly formed Army of Islam (now the largest fighting force in Syria), who works closely with al-Nusra Front.
Via WSJ:
The U.S. and its allies have held direct talks with key Islamist militias in Syria, Western officials say, aiming to undercut al Qaeda while acknowledging that religious fighters long shunned by Washington have gained on the battlefield.
At the same time, Saudi Arabia is taking its own outreach further, moving to directly arm and fund one of the Islamist groups, the Army of Islam, despite U.S. qualms.
Both the Western and Saudi shifts aim to weaken al Qaeda-linked groups, which Western officials now concede are as great a danger in Syria as President Bashar al-Assad’s regime.
Over the past two months, the militias, which command the loyalty of tens of thousands of fighters driving the conflict in Syria, have begun to consolidate their ranks. In late November, they announced they were banding together and forming the Islamic Front.