The United Nations special envoy for Syria has said he intends to bring the government and opposition back to Geneva for a fifth round of talks on March 23 to pursue an agreement to end the six-year war.
Staffan de Mistura told reporters after briefing the Security Council behind closed doors that the UN will be promoting substantive talks on four issues - governance, a new constitution, elections and counter-terrorism, "including the security organisation and confidence-building measures".
He appealed to participants at a meeting in Kazakhstan's capital, Astana, that will take place ahead of the next Geneva talks, to address the challenges of the ceasefire in Syria. Those talks are organised by the three guarantors of the ceasefire - Russia, Iran and Turkey
Russia's military on Tuesday announced a ceasefire until March 20 between rebels and Syria's government in the eastern Ghouta suburbs of the Syrian capital of Damascus, but activists reported a number of air strikes and artillery strikes by government forces and said two civilians were killed.
The announcement from Russia came on the same day top generals from Turkey, the United States and Russia met in Turkey to discuss mutual suspicions over military operations in northern Syria.
Mr de Mistura said it is very important that military commanders of the three countries invested in a solution in Syria meet to avoid conflicts and focus on counter-terrorism. "Without a strong ceasefire, the talks (in Geneva) will be fragile," he warned.
The fourth round of talks ended on March 3.
The US ambassador to the United Nations, Nikki Haley, said the United States supports Mr de Mistura and the UN-led talks, but added that "we do think there are people missing from the table". She did not elaborate but stressed that the United States wants to see an end to the conflict.
"This is very much about a political solution now," Ms Haley said. "That basically means that... Syria can no longer be a safe haven for terrorists."
She added: "We've got to make sure that we get Iran and their proxies out. We've got to make sure as we move forward we're securing the borders for our allies as well, so that they can have confidence in the secure borders."
British Ambassador Matthew Rycroft, the current Security Council president, said all council members support Mr de Mistura and urged the parties at the next round of talks "to engage constructively".
He said Mr de Mistura came across to him during the closed consultations "with some cautious optimism this time - that he had been able to keep all of the different parties at the Geneva talks in the fourth round despite some difficult moments, and there was agreement on these four baskets of issues which will form the agenda for the talks".
Mr de Mistura said he asked the council for support in ensuring that the fifth round goes "upwards" from the fourth - not backwards.
"Above all, I have appealed to all Syrians and outsiders to abandon the fantasies that still are there of a military victory. One side or the other still sometimes believes that is possible. It is pure fantasy," he said.
In the fourth round, Mr de Mistura said, "we did not expect miracles and frankly we didn't have miracles".
"But we achieved much more than many people imagined we could have. No one left. Everybody stayed. They were focused. We got an agenda. We got a timeline. We got some agreements even on substance," he said.
"There is a lot of common ground" on what a Syria settlement could be - but disagreements remain on how to get there, he said.
Mr de Mistura said that in the fifth round, the parties will work in parallel on the four major issues.
"What you should see is four cars who are moving," he said, but the parties must determine how to put "the fuel in each car".