Speaking just hours before the end-of-day deadline for Syria to implement the ceasefire plan, Annan said Syrian forces had withdrawn from some areas but moved to others not previously targeted, and the situation was not as he had hoped.
"I believe it's a bit too early to say that the plan has failed, the plan is still on the table," he told a news conference at the airport in Hatay province in southern Turkey.
"It's a plan we're all fighting to implement,... it's a plan the Syrians have endorsed and from the comments made by the opposition, they're also prepared to go along with it if the government meets its commitments to pull the troops out."
Earlier on Tuesday Syria's foreign minister, speaking in Moscow, said Damascus wanted guarantees from Annan that armed groups attacking its troops would commit to a ceasefire.
And in the meantime on Tuesday, Syrian troops killed 31 people and continued to shell the city of Homs.
"I believe there should be no preconditions for stopping violence. That is something we need to do for the people and for the country concerned," Annan said.
"I had hoped that by now we would have been much further ahead along the road to the government of Syria honouring its commitments and all the parties beginning to take steps to end all violence."
"We still have time between now and the 12th to stop the violence," he added.
Earlier on Tuesday Annan flew by helicopter over the massive refugee camp in Kilis, situated right on the Turkish-Syrian border, where 9,000 Syrians are sheltering and where gunfire from Syria hit Turkish staff and refugees on Monday, drawing a furious response from Ankara.
He later visited one of the first refugee camps to be set up in Turkey last June at Yayladagi, talking with some of those sheltering there.
"To hear their stories, to hear how they came across, how they were shot at, some with their children, was heart-wrenching. But I hope that their courage, strength and patience will pay off soon," he said.
Syrians at the camp danced and chanted Annan's name, urging him to arm the rebel fighters. But there was pent-up frustration too and one refugee threw a shoe at him.
Around 25,000 Syrians have fled the violence and are sheltering in Turkey with hundreds crossing from Syria daily.
Also visiting the Yayladagi camp on Tuesday were US Republican senators Joseph Lieberman and John McCain, both of whom said Annan's plan looked to have failed.
"We respect Mr Annan's desire to find an end to the killing in Syria. Unfortunately, Bashar al-Assad does not share this goal... Indeed, reports indicate that Assad has used the time provided by the recent diplomatic iniative to kill up to 1,000 additional men, women and children in Syria," said McCain.