A senior Syrian opposition official said on Friday that they reject even indirect peace talks with the Assad regime until Russian air strikes stop and regime blockades are lifted from populated areas.
The US Secretary of State John Kerry stated on Thursday peace talks would be held in Geneva next week but they would not be face-to-face.
George Sabra, deputy chief of the opposition delegation, told Reuters, There must be a halt to the bombardment of civilians by Russian planes, and sieges of blockaded areas must be lifted."
"The form of the talks does not concern us, but the conditions must be appropriate for the negotiations," Sabra said.
The opposition will not participate in the indirect talks mentioned by Kerry, he added.
Riad Hijab, the coordinator of the High Negotiations Committee (HNC), said, "all the matters will be tabled clearly."
Moscow wants the opposition delegation to contain groups such YPG, which holds wide areas in northeastern Syria.
On this issue, Sabra stated that the opposition delegation for the talks is chosen by only the opposition council and countries such as Russia had no right to oppose and dictate which opposition groups will be present at the talks.
The opposition council underlined YPG should be classified as on the side of the regime if they are to join negotiations.
The opposition accuses YPG of being in cooperation with Bashar al Assad.
One of the biggest rebel factions, Jaysh al Islam stated that the opposition was facing "many pressures" to make concessions.
"We do not forget that there are sisterly states that support us and help us overcome these pressures, particularly Saudi Arabia, Qatar and Turkey," the group said.
The US, European powers, Turkey and Saudi Arabia back the toppling of Assad regime and support the moderate opposition groups fighting against the regime, while Russia and Iran have been strong allies of Assad whom they provide help, including financial aid and weapons.
The Syrian regime has been laying siege to several towns where thousands of civilians are starving to death, a practice many international figures call a war crime.
According to the UN, more than 250,000 people have been killed since the beginning of the conflict. However, the Syrian Observatory for Human Rights (SOHR) puts the number at more than 350,000.
The war started in Syria in 2001 after peaceful demonstrations demanding freedom and better-living conditions took place.