The World Bank says that 2015 economic growth in the Middle East and North Africa likely came to just 2.6 percent, falling short of a 2.8 percent forecast in October as war, terrorism and cheap oil took their toll.
In a new report, the bank said five years of war in Syria and spillovers to neighbouring countries have cost the region some US$35 billion (NZ$52.15 billion) in lost output measured in 2007 prices, equal to Syria's gross domestic product that year.
The plunge in oil prices to around US$30 a barrel from over US$100 two years ago is causing major problems for the region's oil exporters, with government revenue falling sharply and budget deficits growing.
The World Bank said Saudi Arabia's public debt would reach 20 percent of GDP in 2017, 10 times its level of 2.2 percent in 2013.
"The richest oil exporters in the region, Saudi Arabia, Qatar, Kuwait and United Arab Emirates, have large reserves that will enable them to run deficits over the coming years, although not far beyond that," the World Bank said in the report.
"At current levels of spending, and an oil price of US$40 per barrel, Saudi Arabia will exhaust its reserves by the end of the decade."
The report was issued as the World Bank is in talks on financing with some oil producers in other regions, including Azerbaijan, Nigeria and Angola.
The report cited World Bank estimates of US$3.6 billion to US$4.5 billion in physical damage to just six cities in war-torn Syria: Aleppo, Dar'a, Hama, Homs, Idlib and Latakia. The damage was assessed to housing, health, education, energy, water, transport and agriculture infrastructure.
A similar assessment in Yemen, also hit by war, found US$4 billion to US$5 billion in damage to four cities: Sanaa, the capital, Aden, Taiz and Zinjibar.
But the wars there and elsewhere may be extracting a bigger toll on human capital, as Syrian refugees languish with little or no work, the bank said, while educational gains are being reversed.
More than half of school-age children in Syria were prevented from attending school during 2014-2015, it said.