BEIRUT — Rebel factions in Syria expressed deep reservations Sunday about the terms of a U.S.-Russian deal that seeks to restart the peace process for the war-torn country, with the leader of at least one U.S.-backed rebel faction publicly calling the offer a “trap.”

The second in command of the powerful, ultraconservative Ahrar al-Sham group condemned the superpower agreement as an effort to secure President Bashar Assad’s government and drive rebel factions apart.

“A rebellious people who have fought and suffered for six years cannot accept half-solutions,” Ali al-Omar said in a video statement.

But the commander and other rebel leaders stopped short of fully rejecting the agreement’s interim cease-fire, due to take effect in stages beginning Monday at sunset.

The deal worked out between Secretary of State John Kerry and Russian Foreign Minister Sergey Lavrov in Geneva on Saturday allows the Syrian government to continue to strike at al-Qaida-linked militants, until the U.S. and Russia take over the task in one week’s time.

The arrangement has divided rebel factions, who have depended on the might of the powerful al-Qaida-linked Jabhat Fatah al-Sham faction to resist government advances around the contested city of Aleppo.

Al-Omar said his group would “refuse the targeting of any faction of our blessed factions” and called on rebels to unify into a single front.

Still, a senior official inside Ahrar al-Sham said rebels would nevertheless abide by the cease-fire to regroup after a punishing conflict with pro-government forces over Aleppo.

“The Islamist factions and Jabhat Fatah al-Sham will abide by the cease-fire without publicly declaring it,” the official said. “They will announce they are opposed to the U.S.-Russian agreement, but they will halt their operations on the ground because of the losses they sustained in the battles for Aleppo,” he said, speaking on condition of anonymity.

Other factions less closely tied to Jabhat Fatah al-Sham, including those backed by Turkish ground forces in the northern frontier area, will publicly commit to the agreement, according to the Ahrar al-Sham official.

Under the agreement, the U.S. and Russia will coordinate to target the Islamic State in Syria and Jabhat Fatah al-Sham, while rebels and the Syrian government will be expected to stop attacking one another. The deal has received the endorsement of President Bashar Assad’s government and its key allies.

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