Oil dropped below $100 per barrel after an international energy watchdog expresses "serious concern" about the negative effect of higher prices on the global economy.

Benchmark oil contract fell about 12 percent since setting a two-year high of $113.93 on April 29. The International Energy Agency says oil is still too high and is cutting into household and business incomes. The agency warns that there's "urgent need" for additional supplies to be made available to refineries.

Benchmark West Texas Intermediate crude for June delivery fell $1.11 to $99.43 per barrel in morning trading on the New York Mercantile Exchange. Trading in the June contract ends Friday.

Meanwhile, retail gasoline prices continue to fall, losing another 2 cents overnight to $3.905 per gallon.