A meeting of the International Syria Support Group was "long, painful and disappointing", and the US and Russia failed to agree on how to revive a ceasefire with Syria, according to the UN's mediator for the war-torn country.
However, Syria mediator, Staffan de Mistura, added that it was wrong to declare a cessation of hostilities in Syria dead, and said he wants to believe that Russia and the US are serious about brokering peace.
The meeting was held on the day that Aleppo experienced its heaviest bombardment in months, with shelling by warplanes in rebel-held areas of the city leaving at least 45 people dead as a US plea to halt flights was spurned.
US Secretary of State, John Kerry said that Washington cannot be the only one holding the door open for peace, and urged Russia and the Syrian government to do their part.
"If the Russians come back to us with constructive proposals we will listen," Mr Kerry said at the meeting held on the sidelines of the UN General Assembly.
He added: "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."
Little agreement was reached at the meeting where France demanded Syria ground its planes, the Netherlands said a new Syrian government offensive on Aleppo sends the wrong signal, and Russia said "nothing happened".
"The response of the Russians was not satisfying," FrenchForeign Minister Jean-Marc Ayrault said, while Dutch Foreign Minister Bert Koenders described the Assad offensive as "very negative" which gives out the "wrong signal".
The Syrian Army has also announced the start of a new major offensive in rebel-held eastern Aleppo and called on residents to avoid rebel outposts.
Two million people are caught up in the battle for the Aleppo, which has been split since 2012 between government forces and rebel groups.
A week-long truce, broken on Monday by an attack on an aid convoy, was designed to allow humanitarian access to people trapped in the city.