UN envoy Lakhdar Brahimi says the first two rounds of talks have made little headway but the two sides have agreed to meet again.
Mr Brahimi said: “It 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.”
Points to be discussed in the next round of talks on an unspecified date include violence and terrorism, the transitional governing body, national institutions and national reconciliation.
But Mr Brahimi said the Syrian government had refused to deal with any other points until the issue of combating terrorism was resolved at the talks in Geneva.
Their position had sparked fears on the opposition side that the regime of President Bashar al-Assad did not intend to discuss the transitional governing body at all.
The mediator said: “I think it is better that every side goes back and reflect and take their responsibility. Do they want this process to take place or not?”
Referring to the recent negotiated ceasefire in the city of Homs, he added: “I’m very, very sorry and I apologise to the Syrian people that their hopes which were very, very high that something will happen here.
“I think that the little that has been achieved in Homs gave them even more hope that maybe this is the beginning of the coming out of this horrible crisis they are in.
“I apologise to them that on these two rounds, we have not helped them very much.”
The foreign secretary, William Hague, blamed the Assad regime for the breakdown of Syria peace talks, calling the the lack of progress a “serious setback”.
Mr Hague said: “The failure to agree an agenda for future rounds of talks on the Geneva process is a serious setback in the search for peace in Syria, and the responsibility for it lies squarely with the Assad regime.
“Lakhdar Brahimi’s comments at his press conference this morning made clear that the regime refused to discuss the issue of a Transitional Governing Body, an issue that is at the heart of the negotiation and an essential means of ending the conflict.
“This cannot be the end of the road. With the war in Syria causing more death and destruction every day, we owe it to the people of Syria to do all we can to make progress towards a political solution.
“So we will continue to give our strong support to Lakhdar Brahimi and the Geneva process. It is also now more urgent than ever to move forward with a UN Security Council Resolution that addresses the appalling humanitarian suffering in Syria.
“The people in Syria’s besieged areas and the many parts of the country not receiving any aid cannot wait.”