The prolonged conflict in Syria has already had a devastating economic impact but could yet spiral to cost the country more than $1 trillion, according to a new report.
The report published Tuesday by children's charity World Vision and consultancy firm Frontier Economics said that the Syrian war to date had cost an estimated $275 billion for the country.
It added that real GDP (gross domestic product) per capita was around 45 percent lower than it would have been in the absence of war.
"The $275 billion is just to Syria itself. It's the gap between what the GDP should be and what it is," Fran Charles, World Vision's Syria Response Advocacy Director and one of the writers behind the report, told CNBC by phone from Jordan.
It is money that will never be spent on education, health care, safe environments, livelihoods or a future for children, World Vision added in its report.
The conflict that erupted in March 2011 has resulted in at least 250,000 deaths, with some independent Syrian organizations citing upwards of 450,000 at the start of 2016 – between 11,000 and 19,000 were children, according to World Vision.
Inside Syria alone, the conflict has left an estimated 13.5 million people, including over 6 million children, in need of humanitarian assistance and protection.
"In the best case scenario, even if the war stops this year and it only takes 10 years for the GDP to recover, that will cost Syria between $448 (billion) and $689 billion in terms of lost growth. In the worst case scenario, if the war carries on for another four years to 2020, the GDP takes 15 years to recover and will cost $1.3 trillion," said Charles to CNBC.
Syrian children have paid a high price for this conflict, with between 11,000 and 19,000 children killed, mostly by explosive weapons, reports World Vision.
Among the child survivors in Syria, World Vision estimates that more than 2 million children do not attend school, and 5.7 million are in need of education assistance.
Charles told CNBC that children need not only education but also psychological help to recover from the years of bloodshed they have witnessed.
Parents need support too, and those who have fled the country need to be given legal rights to work so children can go back to school, she added.
"When parents slide further into poverty, that's when the risks increase for children and they are put to work, daughters are sold off into marriage. Parents need to not to rely on child labor," said Charles.
Syria's neighboring countries - Lebanon, Jordan and Turkey - have borne the brunt of the refugee crisis caused by the conflict, with Lebanon the most affected by the Syrian conflict.
The direct cost of Syrian refugees on the Lebanese government budget is estimated at up to $1.1 billion between 2012 and 2014, World Vision said.
"The needs [of Syria] continue to outstrip the resources," said Charles.
The U.S. is the biggest bilateral donor to the region, with the U.K. in second. The U.K. recently pledged to double funding to the crisis to more than $3.2 billion by 2020 to fund education, jobs and humanitarian protection in Syria, Jordan, Lebanon and Turkey, according to The Guardian newspaper.
To reverse the economic cost of the conflict on Syria and the region, a large-scale reconstruction and long-term investment plan is required, Charles believes. Donor countries must not only help bring a political resolution to the conflict, said Charles, but also help Syrians in returning to their country and rebuild.
"Syria can't afford any more years of conflict," she added.