Lakhdar Brahimi, the UN-Arab League envoy to Syria, announced a temporary truce on Wednesday, saying Bashar al-Assad's government will sign up.
The UN Security Council has now unanimously endorsed the ceasefire.
Brahimi also said many rebel groups had agreed, but one of the greatest obstacles of the ceasefire is the division within opposition groups.
The Free Syrian Army - an umbrella term for opposition fighters there - has been described as unco-ordinated, untrained and hampered by infighting.
General Rahal, a senior defector from one of the Syrian government's military academies, talked to Al Jazeera's Anita McNaught in the northern Idlib province about the mistakes that have been made.
"There is no revolution in the whole world without mistakes," he said.