The Syrian opposition delegation in Geneva for a second round of peace talks warned Monday it would not return for a third round if no progress is made.
"If there is no progress at all, I think it would be a waste of time to think about a third round," opposition spokesman Louay Safi told reporters late Monday.
He said the delegation had raised the issue with UN Arab League mediator Lahkdar Brahimi Monday morning, as the second round of talks began.
As long as there is a glimmer of hope that the talks can move forward, "we're not going to run away. We're not going to call it quits," he said, adding though that if there is no progress "let us not pretend we are doing something."
In that case, it would be "more honest to say we have failed," he said -- although he acknowledged the only alternative was to continue fighting the civil war that has already claimed more than 136,000 lives and forced millions from their homes.
Safi's comments came after a rocky first day of talks that saw Brahimi meet separately with the government and opposition teams, in the hope that keeping them apart at first might help achieve more than during a virtually fruitless first round last month.
Syria's warring sides were meanwhile set to sit down for talks together Tuesday, both sides said.
"Tomorrow, at 10 am (0900 GMT), there will be a joint session," Badr Jamous, secretary general of the opposition National Council and member of the delegation, told AFP.
"We are ready to confront the regime at any time and anywhere," he said.
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A source in the delegation of President Basher al-Assad's regime confirmed that there would be a joint meeting Tuesday.
While getting the parties back around the same table can be seen as a step in the right direction, there was no sign that the current round, which is expected to last until Friday, would make progress towards ending the bloodshed.
The two sides spent the day continuing to blame each other for escalating violence on the ground, and neither side appeared prepared to budge an inch on their positions.
With the talks at an apparent standstill, Russia on Monday proposed that Moscow and Washington hold a collective meeting with the United Nations and the two sides to try to move things forward.
United States, which backs the opposition, and Russia, a key ally of Syria, initiated the so-called Geneva II talks and pushed for eight months to get the parties to the negotiating table.
Safi on Monday said that while the opposition was "very disappointed" over Russia's continued support for the Assad regime, it would support the joint talks.
"If this is what it will take to make the regime negotiate a political solution, then we welcome that," he said.
The opposition insists that the only way to put an end to the nearly three years of civil war is to put in place a transitional government -- without Assad.
The Syrian government however insists that the president's future is not up for negotiation.
Instead, the regime insists the talks must focus on stopping violence and "terrorism" -- its term for the revolt, which it says has been fuelled by foreign jihadists and Gulf money.