International efforts to end the Syria war are taking place along two rival tracks, with peace talks due in Geneva on Tuesday overshadowed by a competing process in Astana.
Observers say the UN is battling to compete with Astana's momentum after a deal to create four "de-escalation" zones in the country was agreed on 4 May. Talks in the Kazakh capital began in January, brokered by Russia, Iran, and Turkey.
Since the deal came into effect, fighting has slowed across swathes of the country, but the Assad regime on Sunday secured the evacuation of three rebel-held districts in the capital, bringing it closer to full regime control for the first time since 2012.
The rebel-held district of Qaboun in Damascus had been largely reduced to rubble after weeks of pounding by regime airstrikes.
UN special envoy Staffan de Mistura said last week that he expects the Geneva talks to last four days, with the intention of taking advantage of recent developments.
"After the Astana meeting which took place and which we attended proactively, there has been some outcomes that we find extremely, potentially, promising and we want to connect, as much as possible, that outcome with some political horizon," de Mistura said.
UN-backed talks have generally failed to produce concrete results, but during the last round in March the sides began discussing the issues of governance, a new constitution, elections, and combating "terrorism".
But commentators say the Geneva track is largely symbolic and has been sidelined by Astana talks.
"By design, the Geneva process revolves around this dead-end demand for a negotiated transition," Aron Lund, a fellow at The Century Foundation, told AFP.
"In terms of actually trying to stabilise Syria, the main effect of pegging peace to transition has been to marginalise the UN in Geneva and shift attention to Astana instead," he added.
Delegations for the talks are expected to arrive in Geneva on Monday, including the Syrian regime team headed by its ambassador to the UN, Bashar al-Jaafari.
The Syrian opposition delegation will be represented by the Riyadh-based High Negotiations Committee and led again by Nasr al-Hariri and Mohammad Sabra.
The HNC has continued to call for the removal of Bashar al-Assad as part of any political transition, which has been rejected by the regime.
Astana talks on 'Russian terms'
Assad has dismissed 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.
He has, meanwhile, praised the Astana talks, first sponsored in January by Turkey, which backs the rebels, and regime allies Russia and Iran to reinforce a ceasefire.
"The Astana process doesn't carry the same baggage and is run more on Russia's terms. That means it is more in tune with battlefield realities," Lund said.
Syrian peace efforts have also been marked in recent months by Washington's all-but withdrawal from the process under President Donald Trump.
The previous US administration, in particular then-secretary of state John Kerry, was deeply involved in the Geneva process but since Trump took office Washington has played little apparent role.
According to independent monitors, hundreds of thousands of civilians have been killed in the war, mostly by the regime and its powerful allies, and millions have been displaced both inside and outside of Syria.
The brutal tactics pursued mainly by the regime, which have included the use of chemical weapons, sieges, mass executions and torture against civilians have led to war crimes investigations
