Mr Annan, the former United Nations secretary-general, who has tried to broker an accord, told the UN Security Council that the regime had not pulled its troops and heavy equipment out of towns and cities, as demanded.
He added that Syria was demanding a guarantee that the rebels would lay down their arms and disband, as well as a commitment by regional nations not to arm them.
These requirements were not part of his original plan, he added.
As regime forces continued to shell towns and cities, Britain and other Western powers called for Mr Assad to be censured by the UN.
But with Russia and China still both likely to veto any Western action, the more significant response came from Turkey and Saudi Arabia, which have now emerged as Mr Assad's leading Middle Eastern critics.
The Turkish prime minister, Recep Tayyip Erdogan, announced he was to visit Saudi Arabia on Friday to discuss the crisis and though neither side gave details of any new proposals, reports from Ankara said Mr Erdogan would call for concerted action.
Analysts said Saudi Arabia and other Arab nations are likely to begin the promised release of hundreds of millions of dollars in aid to the rebels, while Turkey's threatened buffer zone came much closer to reality after Syrian troops fired over the border on Monday. (© Daily Telegraph, London)