Syria said on Sunday it wants written guarantees that insurgents will stop fighting before it pulls back troops under a peace plan agreed by President Bashar al-Assad, casting fresh doubt over a truce that is due to happen this week.

The plan, drawn up by U.N.-Arab League envoy Kofi Annan, requires Assad to begin pullback of military concentrations in and around population centres by Tuesday for a truce to start 48 hours later.

While insisting the pullback would happen, Foreign Ministry spokesman Jihad Makdissi released a statement saying earlier reports that Damascus confirmed that it will pull back its troops from and around cities on April 10 is a wrong explanation.

(Annan) has not delivered until now written guarantees regarding the approval of terrorist armed groups to end violence and readiness to lay down its weapons, he said.

Makdissi said that Syria had also requested guarantees that governments of Qatar, Saudi Arabia and Turkey will stop funding the armed groups.

The government and opposition have accused each other of intensifying assaults in the run-up to the truce due to start early on Thursday.

(Reporting by Mariam Karouny; Writing by Robin Pomeroy)