The Algerian-born diplomat said on Saturday that the agreement to evacuate people from the besieged city of Homs had raised hopes that had not been satisfied at the Geneva talks, involving opposition groups and representatives of the Syrian government.
"I am very, very sorry and I apologize to the Syrian people that their hopes, which were very, very high here, that something will happen here," Brahimi told journalists after the talks.
"I think that the little that has been achieved in Homs gave them even more hope that maybe this is the beginning of coming out of this horrible crisis they are in."
Saturday's last session of the second round of the talks was "as laborious as all the meetings we have had, but we agreed on an agenda for the next round when it does take place", Brahimi added.
He said both sides would need to reflect on their responsibilities before round three, and that the government in particular had to accept that the main objective of talks was transition, which has been ruled out by the Syrian government.
The head of the International Committee of the Red Cross (ICRC) also stressed how meager the results had been, saying an evacuation from Homs did not herald any wider improvement in humanitarian access to Syria's civil war zones, where the United Nations says up to 3 million people in need are beyond its reach.
Syria has been gripped by deadly unrest since 2011. According to reports, the Western powers and their regional allies -- especially Qatar, Saudi Arabia, and Turkey -- support the militants operating inside the country.
NTJ/HH