US and Russian plans to end Syria's conflict must be saved as there is no alternative, Russia's Foreign Minister Sergei Lavrov has told the UN.
He was speaking as the northern city of Aleppo endured a day of relentless air strikes, with the Syrian military determined to retake rebel-held areas.
A seven-day US-Russian brokered truce collapsed on Monday.
Mr Lavrov laid the blame on the US for failing to control the rebel groups it backs.
He said a key condition of the truce was for moderate rebel groups backed by the US to separate themselves from militants.