There was also no movement on bringing relief to besieged residents in Syria's central city of Homs, where UN trucks are waiting for access to deliver desperately needed food and medical aid.
After a difficult morning meeting on the fourth day of talks, UN mediator Lakhdar Brahimi said that he had decided to cancel afternoon talks and reconvene the parties for ‘what I hope will be a better session’ today morning.
"Nobody is walking out, nobody is running away," Brahimi told reporters.
“We have not achieved any breakthrough, but we are still at it, and this is good enough as far as I'm concerned,” he added.
A member of the opposition negotiating team, Rima Fleihan, said that Brahimi adjourned the meeting ‘because the regime is not cooperating on any subject, not on humanitarian issues and not on a transitional governing body’.
She said the opposition had presented a preliminary transition plan laying out its ‘vision’ for Syria, but the regime refused to engage in talks.
"We have a vision, unfortunately the regime presented nothing and refused all discussion," Fleihan said.
Tuesday’s session saw delegates from President Bashar al-Assad's regime present a statement it wanted adopted that condemned Washington.
“United States has made a decision to resume arming terrorist groups in Syria,” the statement said.
"This decision can only be understood as a direct attempt to obstruct any political solution in Syria through dialogue," it said.
It follows a report from a leading news agency that US Congress secretly approved funding for weapons deliveries to "moderate" Syrian rebel factions.
Syrian Deputy Foreign Minister Faisal Muqdad said that showed Washington ‘is not interested in the success’ of the peace process.
A State Department spokesman, Edgar Vasquez, dismissed accusations of Washington supporting terrorism as ‘ludicrous’.
"The Assad regime is a magnet for terrorists. The regime's brutality is the source of the violent extremism in Syria today," he said in a statement.
"We support the moderate political and military opposition who are fighting for the freedom and dignity of all the Syrian people,” he added.