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 the United Nations offices 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 4th to create four "de-escalation" zones across some of Syria's bloodiest battlegrounds.
UN special envoy Staffan de Mistura told reporters on Monday that the Geneva talks were working "in tandem" with the Astana process.
Since the Astana 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.
Numerous rounds of UN-backed talks have not produced concrete results, although during the last round in March the sides finally began discussing four separate "baskets" of issues: governance, a new constitution, elections and combating "terrorism" in the war-ravaged country.
Aron Lund, a fellow at The Century Foundation, said that despite Geneva's important "symbolic value, it isn't moving forward in any visible way".
"In practice, the Geneva track has largely been sidelined by the Astana track, at least for now," Lund said.
Delegations began arriving in Geneva on Monday.
The Syrian government team will be headed once again by its UN ambassador Bashar al-Jaafari. The opposition will be represented by the Riyadh-based High Negotiations Committee and led again by Nasr al-Hariri and Mohammad Sabra.
"The key to success in this process is a transition to a free Syria, with no role for Bashar al-Assad or for terrorism," Hariri told reporters in Geneva.
He also welcomed a statement from the US State Department accusing Damascus of destroying the remains of thousands of murdered detainees in a crematorium.
"This is but a drop in the ocean..." Hariri said.
The HNC's continued call for Assad's ouster is seen as a non-starter by the Syrian regime.
"By design, the Geneva process revolves around this dead-end demand for a negotiated transition," Lund told AFP.
"In terms of actually trying to stabilize Syria, the main effect of pegging peace to transition has been to marginalize the UN in Geneva and shift attention to Astana instead," he said.
Rebel backer Turkey and government allies Russia and Iran sponsored the first talks in Astana in late January to reinforce a faltering ceasefire.
They have since returned for several meetings, culminating in the safe zones deal.
Assad has brushed off the upcoming Geneva negotiations as "merely a meeting for the media".
"There is nothing substantial in all the Geneva meetings. Not even one per million. It is null," Assad said in a recent interview with Belarus's ONT channel.
"As to Astana, the situation is different... This started to produce results," Assad said.
De Mistura on Monday downplayed Assad's comments, pointing out that the Syrian president had sent a large, high-level delegation to Geneva, and "they are empowered to serious discussions and they are here to work".
Syrian peace efforts have also been marked in recent months by Washington's all-but withdrawal from the process under President Donald Trump.
But de Mistura said on Monday he was "encouraged by the increasing engagement, the increasing interest, by the US administration in finding a de-escalation".