The newly appointed international envoy for Syria has expressed pessimism about the chances for peace in the war-ravaged country. His remarks follow August bloodshed that claimed an estimated 5440 lives. Speaking in a BBC interview broadcast on Monday, the new UN and Arab League mediator Lakhdar Brahimi said attaining peace in Syria was virtually an insurmountable task. \"I know how difficult it is - how nearly impossible. I can\'t say impossible - nearly impossible,\" Brahimi told the BBC. \"And we are not doing much. That in itself is a terrible weight.\" Brahimi added that he felt as if he was \"standing in front of a brick wall\" looking for any cracks that might provide an opportunity. Brahimi, who replaced Kofi Annan in the post at the end of August, is to visit Damascus this month for talks with Syrian government officials aimed at putting an end to 17 months of violence in the country. Annan stepped down after blaming rifts in the UN Security Council for hampering mediation efforts, including a six-point peace plan. Damascus has announced it will cooperate with Brahimi. \"We will listen to him and he will listen to us,\" said Jihad Makdissi, the Syrian Foreign Ministry spokesman in an interview with a pro-Syrian Lebanese television station. This comes after Syria saw the bloodiest month so far as the government seeks to put down an uprising against President Bashar Assad that began in March 2011. British-based watchdog the Syrian Observatory for Human Rights said on Sunday that altogether 5440 people were killed in August. New \'massacre\' Opposition activists have meanwhile accused government forces of committing a new massacre on the outskirts of Damascus. Pictures posed online showed dozens of piled bodies. The Observatory also claimed that a Syrian warplane has killed at least 18 people in a single attack when it bombed a building in the northern rebel-held town of Al-Bab in Aleppo province. \"The victims included two children, a girl and a boy,\" Rami Abdel Rahman, the director of the Observatory, told the AFP news agency. \"They died when the fighter jet bombed the building where they were sheltered.\" The airstrike followed a series of attacks on towns and villages in the region as regime forces try to cut off rebel supply lines to the northern city of Aleppo, a major battleground in the conflict. The Observatory says more than 26,000 people have now died since the outbreak of the anti-regime revolt. Casualty figures cannot be independently verified, as Syria does not allow free access to journalists.