Russian Foreign Minister Sergei Lavrov lashed out at the U.S. Friday, accusing it of using Syrian peace talks in Geneva for the sole purpose of "regime change."
His comments suggested a meeting between senior U.S. and Russian officials in Geneva a day earlier had not gone well.
"The only thing they want to talk about is the establishment of a transitional governing body," Lavrov said.
"Only after that are they ready to discuss the urgent and most pressing problems, like terrorism," he added, speaking after meeting with the German foreign minister in Moscow.
Lavrov said the Russia-U.S. initiative for the talks in Geneva clearly stated that discussions must not have artificial time constraints or deadlines.
"Now they are saying that to keep talking is senseless, because the government [of Syria] doesn't want to agree about the makeup of a transitional governing body. We are going in circles," Lavrov said.
A second round of peace talks in Geneva has yielded little more than acrimony. Violence has escalated on the ground and delegates have not agreed on an agenda for the talks. The opposition and its U.S. backers insist the aim of the talks is to agree on a transitional governing body to administer the country until the next elections.
The Syrian government delegation says halting "terrorism" should be the priority, and rules out talk of transition while the violence rages.
After meeting separately with the Syrian government and opposition delegations on Friday,
International mediator Lakhdar Brahimi apologized to the Syrian people on Saturday for the lack of progress at peace talks in Geneva after their second round ended with little more than an agreement to meet again.
The aim of the talks is to end the conflict which has killed more than 130,000 people and displaced millions in three years.
Brahimi said 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 President Bashar Assad.
The head of the International Committee of the Red Cross, or 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.
"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.
Opposition National Coalition spokesman Louay Safi said there was "nothing positive" to take from round two, which lasted a week. The final session lasted around half an hour.
Syrian government delegate Bashar al-Jaafari, said the opposition wanted the issue of "terrorism" to stay open-ended. "Whoever refuses to fight terrorism is part of terrorism," he told reporters after the final session.
Material from Reuters is included in this report.