Russia and Iran have a key role in the efforts to end the bloodshed in Syria, international envoy Kofi Annan said Sunday, while adding that so far his work to bring peace has failed.

The UN-Arab League envoy told France's Le Monde daily that the 16-month carnage in Syria showed no sign of ending and there was no guarantee that his mediation would bear fruit.

"It's been three months since I have been involved," he said in an interview published in French.

"Great efforts have been made to try and resolve this situation in a peaceful manner with a political solution," he said. "Evidently, we have not succeeded. And maybe there is no guarantee that we will succeed."

- Agence France Presse