Syrian opposition members met for a third day Thursday to decide whether to attend UN peace talks, with less than 24 hours before the negotiations were due to open in Geneva.
The Saudi-backed High Negotiations Committee -- formed last month in an effort to unite Syria's fractious political and armed opposition -- said it was waiting for clarifications from the United Nations before agreeing to attend the talks, which were to open on Friday in the Swiss city.
Western diplomats have piled pressure on the opposition to take part in the negotiations, part of the biggest push yet to resolve Syria's nearly five-year civil war.
But after two days of meeting in the Saudi capital the Committee, which was formed to lead negotiations and insists it alone must represent the opposition, had yet to agree to participate.
The Committee has asked for "clarifications" after the UN issued invitations to other opposition figures and is demanding assurances from the international community that it will move to end regime attacks on civilians and allow humanitarian aid.
Salem al-Meslet, a Committee spokesman, said it was waiting for an answer from UN Secretary General Ban Ki-moon on the application of a Security Council resolution adopted in December that endorsed a roadmap for peace.
- Seeking answers from UN -
He said UN Syria envoy Staffan de Mistura had already assured the opposition that two of the resolution's articles -- calling for immediate access for humanitarian aid and an end to attacks on civilians -- were non-negotiable.
Security Council members "must take their responsiblities and commit to applying resolution 2254. We are waiting for an answer," Meslet said.
"We are serious about participating in the negotiations, the ones who are hindering the start (of talks) are those who are bombing and starving civilians."
The talks are part of a UN-backed plan, agreed by top diplomats last year in Vienna, that envisages negotiations followed by a transitional government, a new constitution, and elections within 18 months.
The roadmap is the most ambitious plan yet to end the conflict which has killed more than 260,000 people and forced millions from their homes.
- 'Russian strikes' kill 44 -
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Instead of meeting face-to-face, Geneva delegations are expected to engage in indirect negotiations.
Officials have said the talks, only the second dialogue between Syrians since the start of the conflict, would run over six months, with the first round expected to last between two and three weeks.
Syria's regime has designated its UN envoy Bashar al-Jaafari as its chief negotiator.
US Secretary of State John Kerry met with Committee members in Riyadh at the weekend and Washington has kept up the pressure on them to attend.
State Department spokesman Mark Toner said Wednesday the talks were a "historic opportunity" and urged the opposition to take part.
"It should seize this opportunity to test the regime's willingness and intentions and expose before the entire world which parties are serious about a potential peaceful political transition in Syria and which are not," he said.
De Mistura's office said on Tuesday it had issued invitations to the talks, but refused to say who had been invited.
The Committee, which earlier this month named Mohammed Alloush of the Islamist rebel group Army of Islam as its chief negotiator, confirmed it had received an invitation, but so did several other opposition figures not belonging to the body.
It was unclear whether the others had been invited as official delegates or as observers.
Russia, a key Assad ally, has called for broader opposition representation at the talks while Ankara has warned against any participation of Kurdish forces it says are linked to Turkey's outlawed Kurdistan Workers' Party (PKK).
There have been no suggestions that jihadist movements, including the Islamic State group which has seized control of large parts of Syria and neighbouring Iraq, should be invited.
The push for talks comes as Syrian forces have been making advances against rebels in various parts of the country, thanks in large part to Russian air strikes launched in September.
Critics have accused Moscow of killing hundreds of civilians in the strikes and on Thursday a monitor said at least 44 civilians had died in suspected Russian air raids in parts of northern and eastern Syria under IS control.
The Syrian Observatory for Human Rights said the strikes on Wednesday had killed 29 civilians in villages in the eastern Deir Ezzor province and its provincial capital, and another 15 civilians in and around the city of Al-Bab, an IS bastion in the northern province of Aleppo.