The International Committee of the Red Cross (ICRC) estimates that about 90% of Syrians live below the poverty line.
"Nearly 90% of Syrians live below the poverty line with more than 15 million needing humanitarian assistance, a trend that has been sustained over the past years," the ICRC said in a statement.
"The risk of collapse of Syria's critical infrastructure is a pressing concern," it added.
Syria has been mired in a vicious civil war since early 2011 when the Bashar al-Assad regime cracked down on pro-democracy protests with unexpected ferocity.
"The international community must confront the harsh reality that the current situation in Syria is untenable," Fabrizio Carboni, the ICRC's regional director for the Near and Middle East, said.
"Failure to act will have dire consequences for all those involved and hinder any prospects for sustainable recovery," he added.
The ICRC appealed to donor states for "an immediate international commitment to safeguard critical infrastructure and essential services."
It also called for ensuring that "a comprehensive humanitarian response can be sustained while more durable solutions can be found."
"Coordinated efforts and increased funding are urgently needed to facilitate early recovery," the organization said.
