Russian President Vladimir Putin said yesterday that he could not be sure attempts to persuade Syria to surrender its chemical weapons would succeed.
He spoke as the weekend deadline for the regime to produce a list of its arsenal approached.
"Whether it will be possible to see this through to the end, I can't say 100 per cent," he said, adding that recent events "inspire confidence that it will be done".
His comments came after President Bashar al-Assad denied using chemical weapons but promised to act quickly to make information available and to open chemical weapons facilities to international inspectors.
Assad also said in a US television interview that he was fully committed to the disarmament, but the US should consider paying some of the cost. He warned that the process would take up to a year and could be environmentally damaging.
The White House labelled Assad's denial of responsibility for the attacks "farcical".