European leaders urged Russian President Vladimir Putin to use his country's influence to support a lasting ceasefire in Syria so that work can begin on a long-sought political solution to the five-year-old war.
German Chancellor Angela Merkel and French President Francois Hollande, who met in Paris, telephoned Friday with Putin, nearly a week after a temporary truce went into effect.
"I want to emphasize that the commitment to a ceasefire is an important message that was confirmed by the Russian president," Merkel said, noting exceptions for military operations against the Islamic State and al-Qaeda's Syria branch, al-Nusra Front.
The Kremlin could use its clout with Damascus - Moscow's most important ally in the region - to keep the ceasefire on track, Merkel suggested after the call, in which British Prime Minister David Cameron and Italian Prime Minister Matteo Renzi participated.
"We all agreed that the political process must begin as soon as possible, because it will be the foundation for a transformation," Merkel said.
A US-Russian brokered ceasefire went into effect a week ago, and while it has been marred by breaches, UN Syria mediator Staffan de Mistura said this week that there has been a "visible" reduction in violence and that critical aid shipments had reached conflict areas.
"The main point that the European leaders made on the call to Putin was that we welcome the fact that this fragile truce appears to be holding," a spokeswoman for the British prime minister said.
The current "positive dynamic" in Syria must be capitalized on "to move from a truce into a more lasting durable peace," the Downing Street spokeswoman said of the 50-minute phone call.
"It was noted with satisfaction that the ceasefire regime is being observed on the whole, is bringing its first positive results and, most importantly, is creating an atmosphere for launching a political process in Syria," the Kremlin said in a statement.
UN-sponsored peace talks on Syria are scheduled to restart in Geneva on Wednesday after they were suspended last month amid a Russian-backed Syrian government offensive around the city of Aleppo that triggered an exodus of tens of thousands of civilians.
US deputy secretary of state Antony Blinken told dpa in an interview late Friday in Paris that the ceasefire was "very, very fragile, but there is hope" both on the political track and in provision of humanitarian relief to hundreds of thousands of civilians in besieged areas in Syria.
"Now the question is, having made that progress: If it's sustained over the coming days, that creates a foundation on which to resume negotiations toward a political transition, and that's the next step," Blinken said.
Foreign ministers from France, Germany and Britain met in Paris on Friday.
"This cessation of hostilities is fragile, and we have to build from what we have to a point, hopefully, in the future, when the moderate opposition and the forces currently behind the regime are working together against Daesh," British Foreign Minister Philip Hammond said, using an alternate name for the Islamic State.
They said that upholding the ceasefire and allowing access to humanitarian aid was vital to ensure peace talks in Geneva continue.