The UN's World Food Program (WFP) suspended aid to more than 1.7 million Syrian refugees in neighboring countries on Monday, due to lack of funds.
The program allowed Syrian refugees in Lebanon, Jordan, Turkey, Iraq and Egypt to buy food from local shops with vouchers provided by the WFP.
Many families will go hungry through the winter if donors fail to pledge an additional $64 million to cover the aid for December, the WFP said.
The agency has so far spent about $800 million feeding refugees since Syria's civil war erupted in 2011.
A lack of food will "potentially cause further tensions, instability and insecurity in the neighboring host countries," WFP Executive Director Ertharin Cousin said in a statement.