Echoing the position of the rival camps, senior US and Russian officials traded accusations over who was to blame for the stalemate, adding to the polarization of a war that has killed 1,30,000 people, displaced millions, destroyed a country and threatens to engulf the Middle East in religious conflict.
It was unclear today how long the weary sides were willing to continue with the talks, which have been on the verge of collapse since they were convened last month. Despite the rancor, both sides left the door open for more negotiations, including a possible final session Saturday before breaking up.
Both the US and Russia have kept the talks going, knowing that it was the only option on the table, at least for now.
The rebellion against Assad's rule has been sapped by deadly infighting among moderates, Islamic groups and al-Qaida-inspired militants competing for control of territory, weapons and influence. Assad's forces are solidifying gains, but the battle lines are largely stalemated, leading to a growing sense internationally that neither side is close to victory.