A boy rides a bicycle past a man sitting on rubble of a damaged house in the rebel held historic southern town of Bosra al-Sham, Deraa.

Russian warplanes continued bombing Syrian rebel-held areas in northwestern Syria and government forces also pounded a suburb of the capital on Thursday, ahead of a planned halt to fighting that rebels predicted Damascus and Moscow would ignore.

The “cessation of hostilities” agreed to by the United States and Russia is due to take hold on Saturday morning from midnight. But opponents of President Bashar al-Assad say they expect the government to press on with its advance, by branding opposition fighters al Qaeda militants unprotected by the truce.

Damascus has agreed to the deal, as has the main opposition alliance, although it is only ready to commit for two weeks given its deep reservations. But the government and its allies will be permitted to forge on with strikes against militants of ISIS and an al Qaeda-linked group, the Nusra Front.

The government also says the agreement could fail if foreign states supply rebels with weapons or insurgents use the truce to rearm.

U.S. President Barack Obama said on Thursday the United States was resolved to try to make the deal work but that “there are plenty of reasons for scepticism.”

Saying the Syrian government and Russia must live up to their commitments, Obama told reporters after meeting with his national security team: “The coming days will be critical and the world will be watching.”

Ending the conflict in Syria, he added, could allow all parties to focus on the fight against ISIS.

Fighting in the final days before the truce has focused on Daraya, a besieged suburb of the capital held by fighters the government describes as Nusra militants but rebels say are from other groups, and on the northwest near the Turkish frontier.

Four months of Russian air strikes turned momentum Assad’s way in a 5-year-old war that has killed more than 250,000 people, created the world’s worst refugee crisis and seen ISIS fighters declare a “caliphate” in Syria and Iraq.

The multi-sided civil war has drawn in most regional and global powers, with Western countries, Arab states and Turkey forming a coalition against ISIS while also backing rebels fighting to overthrow Assad. Russia and Iran support him.

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