Syrian government and opposition delegates in Geneva said peace talks have reached an impasse, with no progress on ending the three-year civil war..
United Nations mediator Lakhdar Brahimi met separately Friday with the Syrian government delegation and the opposition delegation.
Syrian opposition spokesman Loay Safi said Friday the five days of negotiations had come to a "dead end'' because of the government delegation's "belligerence.'' Syrian Deputy Foreign Minister Fayssal Mikdad said the opposition came to the talks with an "unrealistic agenda.''
Both sides kept open the possibility for more negotiations.
The United States, which supports the rebels, and Russia, which supports the Syrian government, have both criticized the deadlock.
Secretary of State John Kerry said during a visit to Beijing Friday the U.S. is concerned the Geneva talks are not producing the kind of discussion on a transition government that is needed. He said U.S. President Barack Obama has asked people in his administration to think about various options for Syria "that may or may not exist."
The opposition earlier this week proposed a transitional government, in a plan that avoided any mention of Syrian President Bashar al-Assad.
Many viewed the move as a concession, since the opposition has insisted it would be satisfied with nothing short of President Assad's removal.
But Damascus refused to even discuss the plan, saying it was a distraction from discussing combating terrorism - what it views as the talks' main purpose.
Russian Foreign Minister Sergei Lavrov accused the United States of using the peace talks for the sole purpose of a Syrian "regime change."
The U.N. Security Council continues discussions Friday on a draft resolution that, among other things, expresses "grave alarm" over civilians trapped by Syrian forces.
Russia, Syria's main ally, is threatening a veto, calling it too one-sided against the Syrian government.
U.N. emergency relief coordinator Valerie Amos said Thursday getting aid to desperate civilians in Syria should not be a matter of controversy or politics.
In Syria, thousands of civilians have fled the rebel-held town of Yabroud after the Syrian government rocked the area with bombings and shelling.