Diplomatic attempts to end the Syrian conflict are "nearly impossible" and not enough is being done to end the fighting, the new UN and Arab League mediator Lakhdar Brahimi has said.
Speaking in a BBC interview, he said: "I know how difficult it is - how nearly impossible. I can't say impossible - nearly impossible".
"And we are not doing much. That in itself is a terrible weight."
Mr Brahimi replaced Kofi Annan as the United Nations and Arab League joint special representative on Syria at the end of August.
Mr Annan stepped down after blaming "finger-pointing and name-calling" at the UN Security Council for hampering efforts to find a breakthrough in the conflict.
Around 20,000 people have been killed during a 17-month uprising against Syria's President Bashar al-Assad.
Mr Brahimi said he was "scared of the weight of responsibility" on his shoulders and was aware that not enough is being done to end the violence through diplomacy.
"People are already saying 'People are dying and what are you doing?' And we are not doing much. That in itself is a terrible weight," he said.
Mr Brahimi said he felt like he was "standing in front of a brick wall", looking for cracks that may yield a solution.
"I'm coming into this job with my eyes open, and (with) no illusions," he said.
Elsewhere, a car bomb has exploded in a religiously mixed district on the edge of the Syrian capital, Damascus.
The state news agency SANA said that the injured included women and children.