There was also no movement on bringing relief to besieged residents in Syria's central city of Homs, where U.N. trucks are waiting for access to deliver desperately needed food and medical aid.
After a difficult morning meeting on the fourth day of talks, U.N. mediator Lakhdar Brahimi said he had decided to cancel afternoon talks and reconvene the parties for "what I hope will be a better session" on Wednesday morning.
"Nobody is walking out, nobody is running away," Brahimi told news hounds after cutting short a fourth day of talks aimed at ending the bloody civil war that has claimed 130,000 lives.
The U.N.-Arab League
...an organization of Arabic-speaking states with 22 member countries and four observers. The League tries to achieve Arab consensus on issues, which usually leaves them doing nothing but a bit of grimacing and mustache cursing...
envoy stressed that neither party bore the blame for his decision to cancel Tuesday's afternoon session after morning talks remained stuck.
"We have not achieved any breakthrough, but we are still at it, and this is good enough as far as I'm concerned," Brahimi said, adding that he was hoping for "a better session tomorrow (Wednesday) morning".
His comments followed a flurry of statements from both sides blaming the other for obstructing the morning's talks, which were marked by the regime delegation's harsh condemnation of a report that the U.S. Congress had secretly approved funding for weapons deliveries to "moderate" Syrian rebel factions.
Brahimi rejected the regime's contention that the United States, which along with Russia instigated the peace talks, was not dedicated to their success.
"I believe that they are serious and they want this track to be successful... There is no doubt concerning that," he said.
A member of the opposition negotiating team, Rima Fleihan, told Agence La Belle France Presse 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 morning's session saw delegates from
Hereditary President-for-Life Bashir Pencilneckal-Assad
The Scourge of Hama...
's regime present a statement it wanted adopted that condemned Washington.
The statement, obtained by Agence La Belle France Presse, said "the United States has made a decision to resume arming terrorist groups in Syria."
"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 the Rooters news agency that the U.S. 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 grinding of the peace processor.
A State Department front man, 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."
Delegates from the regime and the opposition National Coalition have been brought together in the biggest diplomatic push yet to end a civil war that has left more than 130,000 dead and forced millions from their homes.
Expectations are low for a breakthrough, especially after the talks hit an impasse Monday when the two sides failed to agree on even the basic principles of political talks.
Despite their frustration, each side vowed it would not be the first to walk away from the talks, which are expected to last until Friday.
In the only tangible promise to emerge from the meetings so far, Brahimi said Sunday the regime had agreed to allow women and kiddies safe passage from besieged rebel-held areas of Homs.
But there has been no movement since, on either an evacuation or Brahimi's hope that aid convoys will be allowed in the areas.
The Old City of Homs has been under siege since June 2012 after rebels there rose against the regime, with an estimated 500 families living with near-daily shelling and the barest of supplies.
U.N. bodies and the International Committee of the Red Thingy have said they are on standby with aid but are waiting for approval to move in.
"The convoy is ready and still waiting to enter. The authorization has not been given yet," Brahimi said. "We haven't given up on that."
Activists in Homs on Tuesday urged opposition figures at the talks to push for the lifting of the 600-day siege.
"We need the siege lifted and to ensure that residents can enter and exit through safe corridors, without passing through regime checkpoints," the activists said in a statement.
Should the siege remain in place, "all solutions will be futile, and will do nothing to end this tragedy," they said.