UN Syria mediator Staffan de Mistura described the talks as "long, painful and disappointing", but said all hope is not lost
A high-level meeting between the United States and Russia failed to reach an agreement on how to revive the Syrian ceasefire that has come under attack from all sides.
After the meeting in New York on Thursday, US secretary of state John Kerry said all parties must show intent to move forward.
He said Washington cannot be the only one trying to hold open the door.
"If the Russians come back to us with constructive proposals we will listen," Kerry said.
He urged Russia and the Syrian government to do their part to restore the truce.
"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 United States on Wednesday had asked both Russia and Syria to ground warplanes to allow truce a chance.
But Kerry said he received no such promise from them to ground planes and to halt the bombardment in Syria.
"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.
"Not for one day or two, but for as long as possible so that everyone sees that they are serious."
Kerry assured that the peace talks will continue despite the setback in the International Syria Support Group meeting.
"Make no mistake, the United States will continue to pursue every avenue of progress that we can because it is the only way to stop the killing, it is the only way to ease the suffering and it's the only way to make possible the restoration of a united Syria," Kerry said.
Kerry is ready to meet his Russian counterpart Sergei Lavrov again on Friday to take the talks forward.
Meanwhile, other leaders at the meeting described the talks as "long, painful and disappointing."
UN Syria mediator Staffan de Mistura said it was wrong to declare the cessation hostilities in Syria dead.
The peace envoy for Syria added that he wants to believe that Russia and the United States are serious about brokering peace.
(WION with inputs from agencies)