Experts at the International Energy Agency have dramatically pushed back their view on when oil prices will rebound from current 13-year lows, saying the supply glut will hold prices down until early next year.

A year ago, the IEA, a Paris-based organization of 29 major oil importing nations, had forecast a "relatively swift" recovery. Instead, oil prices have continued to fall, reaching a level below $30 a barrel last seen in 2003, the IEA says in its latest report Monday.

IEA chief Fatih Birol blamed "extraordinary volatility" in oil markets that has made forecasting "more difficult than ever" for its changed outlook.

In its report, the agency says oil supplies have surged due to a three-year rise in stocks, a phenomenon last seen in the mid-1990s.