US Secretary of State John Kerry said his Russian counterpart had not been able to promise to ground Syria's bombers and to halt the bombardment of its cities.
"The question now is whether there remains any real chance of moving forward, because it is clear that we cannot continue on the same path any longer," Kerry said.
"The first thing that we have to do is find a way to restore credibility to the process, if that can be done," he said, of attempts to restore the ceasefire.
"The only way to achieve that is if the ones that have the air power in that part of the conflict simply stop using it," he said as the meeting in New York broke up.
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"Not for one day or two, but for as long as possible so that everyone sees that they are serious."
Kerry, Russia's Foreign Minister Sergei Lavrov and envoys from the other 21 nations of the International Syria Support Group are in New York for the UN General Assembly.
The US diplomat said he was ready to meet Lavrov again on Friday to see if anything could be done.
But the UN peace envoy for Syria, Staffan de Mistura, was downbeat, calling it a "long, painful and disappointing meeting."
France's Foreign Minister Jean-Marc Ayrault added that Russia had not been able to provide a satisfactory response to calls for Syria to ground its jets.