Main opposition group was threatening on Sunday to walk away before planned peace talks even begin in earnest

Main opposition group was threatening on Sunday to walk away before planned peace talks even begin in earnest.

Representatives from the umbrella body for mainstream opposition groups, who arrived in Geneva late Saturday, are refusing for now to enter the hoped-for talks with the Syrian government.

The High Negotiations Committee (HNC), set to meet with U.N. envoy Staffan de Mistura on Sunday, are demanding that humanitarian aid first gets through to besieged towns, that “bombing of civilians ceases and that hundreds of prisoners are released.”

"If the regime insists on continuing to commit these crimes then the HNC delegation's presence in Geneva will not be justified," coordinator Riad Hijab warned in a statement in Arabic posted online Saturday.

"The delegation will inform de Mistura of its intentions to withdraw its negotiating team if the UN and world powers are unable to stop these violations," he said.

A fresh spat between Russia and Turkey, two of the many outside powers embroiled in the conflict, erupted Saturday after Ankara accused Moscow of “violating its airspace” two months after it shot down a Russian jet.