"The beginning of this week is as laborious as it was the first week," Brahimi told reporters after the warring sides held their first face-to-face talks since the second round of negotiations opened yesterday.
"We are not making much progress."
The new round of the so-called Geneva II talks got off to a shaky start yesterday and there was little sign that today's face-to-face meeting had seen more than a restating of positions.
"The regime is not even budging on this, insisting that they want to talk about one thing," said opposition spokesman Louay Safi.
The regime insists Assad's future is non-negotiable and that the talks must focus on halting "terrorism" -- its term for a revolt it says is fuelled by foreign jihadists and Gulf money.
Deputy foreign minister Faisal Muqdad said the government was ready to discuss all points but that terrorism must top the agenda.
Brahimi appealed to all parties to "help Syria out of the nightmare its people have been living through now for three years".
But he added: "I'm not sure whether I can impose an agenda on people who don't want. How can you put a gun on their heads? It is their country."
An eight-day session last month achieved little beyond getting the foes into the same room for the first time since the conflict erupted in March 2011.
