BEIRUT — Rebel factions in Syria expressed deep reservations on 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,” said Ali al-Omar in a video statement.

But the commander and other rebel leaders stopped short of fully rejecting the interim cease-fire, which is slated to come into effect in stages beginning at sunset Monday.

The deal announced Saturday that was hammered out by U.S. Secretary of State John Kerry and Russian Foreign Minister Sergey Lavrov 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, formerly known as the Nusra Front, 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 abide by the cease-fire to regroup after a punishing conflict with pro-government forces over Aleppo.

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 terms of 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 — Russia, Iran and the Lebanese militant group Hezbollah.

But that scenario is complicated by the fact that Jabhat Fatah al-Sham remains intertwined with several other factions.

It is not clear how those governments intend to distinguish between Jabhat Fatah al-Sham and other rebel factions or how they will be able to attack the al-Qaida-linked militants without hitting other rebels as well.

Over 2,000 people have been killed in fighting over the past 40 days in Aleppo, including 700 civilians and 160 children, according to a Syrian human rights group.

One of the more immediate goals of the Kerry-Lavrov agreement is to allow the United Nations to establish aid corridors into Aleppo.