The conflict in Syria has more than halved the amount of oil the Middle Eastern country can supply, the Organization of the Petroleum Exporting Countries (OPEC) said on Tuesday.
The influential oil exporters' group also said that demand for oil had risen this year as the picture for the global economy improves. OPEC revised its demand forecasts up by 25,000 barrels a day in 2013.
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A subdued improvement in developed world economies, such as the U.S. and Europe, has offset a slowdown in emerging and developing economies, according to OPEC.
"Risks to the forecast remain high due to weather, natural decline, technical, political and environmental factors," the group warned.