Geneva: Talks to end Syria's brutal five-year conflict were rattled on Thursday by uncertainty surrounding the arrival of a second opposition group and the declaration by Syria's Kurds of an autonomous region.
UN mediator Staffan de Mistura met for the first time late on Wednesday with an umbrella delegation including the so-called Moscow Group, which is demanding an equal seat at the negotiating table in Geneva.
But such a move would be hotly contested by the "official" opposition High Negotiations Committee (HNC), a broad collection of political and armed opposition factions which joined forces in Riyadh last December.
The HNC is due to have a second official meeting with de Mistura on Thursday, where it is expected to insist on its demand to remain the sole opposition representative in the talks.
"That is one of the most important points," a Western diplomat told AFP, requesting anonymity.
The entry into the talks of the Moscow Group, along with the so-called Cairo and Istana groups, followed Russia's surprise decision this week to withdraw most of its forces from Syria, where they had been fighting in support of President Bashar al-Assad.
Western governments had voiced hopes the pullout, expected to be completed by the end of the week, could boost the talks by pressuring Assad.
But Russian President Vladimir Putin said Thursday his country could ramp up its presence again if needed "literally within several hours".
In Geneva, it was not immediately clear what impact the inclusion of the pro-Moscow group would have on the talks, or whether it was a gesture from de Mistura to Russia following the pullout.
The UN has not yet clarified what role the Moscow Group would play but its co-president Randa Kassis told reporters Wednesday her camp was in Geneva "as a negotiating delegation".
Jihad Makdissi, a member of the Cairo group, told AFP Thursday: "We will sit at the table as two (opposition) delegations," adding that de Mistura had agreed to meet again with the new delegation in the coming days.
The Moscow Group is tolerated by Damascus and has not insisted on Assad's departure as a condition for creating a transitional government, which is an unequivocal HNC demand.
The HNC and the Western powers that support it meanwhile insist only one opposition delegation and one government delegation can actually negotiate.
The Moscow Group has no troops on the ground in Syria, and is being put forward to "support the idea that there is no united opposition and to cast doubt on HNC's legitimacy," the Western diplomat said, adding that adding a second opposition delegation was "a highly contentious issue."
Adding another level of complexity to the difficult talks, Kurdish parties so far excluded from the negotiations in Geneva on Thursday declared a federal region in areas under their control in northern Syria, as they seek further autonomy.
A wide range of critics have warned this could threaten efforts to forge a united Syria.
Speaking ahead of the Kurdish declaration, de Mistura branded the federalism push as possibly "dangerous", according to the Swiss news agency ATS.
The Moscow Group said it was working to "lift the embargo" against bringing in Kurdish delegates, while a member of the Syrian government delegation told AFP the Kurds would be "invited to the talks in the next stage".
Despite the intricate web of interests surrounding the talks, observers say the current round of dialogue is taking place in a far more constructive atmosphere than during multiple previous failed peace efforts.
The talks, currently indirect, follow a ceasefire between the government and some opposition groups introduced on February 27 that remains broadly in place.
"The talks have entered a more serious stage," the regime delegation source said.
De Mistura has voiced tentative optimism, backed by US Secretary of State John Kerry who heads to Moscow next week to discuss the peace drive.
"We may face the best opportunity that we've had in years to end (the war)," Kerry said Tuesday.
The conflict has killed more than 270,000 people and send millions fleeing, many seeking new lives in Europe where the influx of refugees and migrants from the Middle East, Africa and Asia has created a huge headache for the EU.