Syria has promised to observe a UN-backed ceasefire starting on Thursday, but its forces have kept up fierce attacks on opposition neighbourhoods in the hours before the deadline.
A Syrian defence ministry source who was quoted on state television on Wednesday said the army would halt operations on Thursday morning, but would confront "any assault" by armed groups.
Our Senior Correspondent Paul Davies reports on the prospect of a truce:
UN-Arab League envoy Kofi Annan said the Syrian government had also assured him it would stop fighting by the dawn deadline he has set for a cessation of hostilities.
It agreed "to cease all military fighting throughout Syrian territory as of 6 am (0300 GMT) tomorrow, Thursday, 12 April, 2012, while reserving the right to respond proportionately to any attacks carried out by armed terrorist groups against civilians, government forces or public and private property", Annan's spokesman Ahmad Fawzi said in a statement, quoting a letter from the Syrian Foreign Ministry.
Russia, a powerful defender of President Bashar al-Assad against Western and Arab pressure, said the rebels battling to oust him must honour the ceasefire too.
Insurgents, who lack a clearly coordinated command structure, have previously said they will stop shooting if Syrian forces pull back and observe the truce as promised.
But few in the Syrian opposition believe Assad has any intention of complying with Annan's plan to end 13 months of bloodshed.
At least 12 people were killed on Wednesday, activists said.
Western powers, too, have scorned Assad's truce pledges, but so far lack an effective policy to curb the bloodshed, given their own aversion to military intervention and the resistance of Russia and China to any UN Security Council action.
"Far from fulfilling their commitment, the regime has cynically exploited the window of diplomatic negotiations to crack down even harder on its own people," Prime Minister David Cameron said during a visit to Indonesia.