A new round of Syrian peace talks opens in Geneva on Tuesday, overshadowed by a competing process in Astana and with rebels reeling from a major setback in Damascus.
Since it broke out in March 2011, Syria's conflict has killed more than 320,000 people, displaced millions and ravaged the country's economy and infrastructure.
Efforts to end the war are now proceeding along two rival tracks: the formal political peace process hosted at United Nations headquarters in Geneva and, since January, parallel talks in Kazakhstan brokered by Russia, Iran and Turkey.
Observers say the UN appears to be scrambling to match Astana's momentum after a landmark deal signed in Kazakhstan on May 4 that would create four "de-escalation" zones across some of Syria's bloodiest battlegrounds.
Since the deal came into effect a week ago, fighting has slowed across swathes of the country.
But in Damascus, which is not included in the deal, the government has secured the evacuation of three rebel-held districts, bringing it closer to exerting full control over the capital for the first time since 2012.
Briefing journalists last week in Geneva, UN special envoy Staffan de Mistura stressed the "rather business-like, rather short" nature of the upcoming talks, expected to last just four days in order to "hit the iron while it's hot".