Oil prices settled Thursday below 100 U.S. dollars a barrel for the first time in 2012 after report said that the European Union may delay its sanction on Iran oil.

Report showed that a lot of EU countries were pushing for a delay of the region's embargo on Iranian oil, fearing that rising oil prices would have an adverse effect on their debt-stricken economies.

According to the report, EU countries receive 18 percent of Iranian crude exports, with Italy, Spain and Greece heading the list.

Before plunging at the news, oil went higher in early session as a major union threatened to stop the country's crude oil production as part of a nationwide strike and protests.

As of Thursday's close, light, sweet crude for February delivery dropped 1.77 dollars, or 1.75 percent, to settle at 99.10 dollars a barrel on the New York Mercantile Exchange.

In London, Brent crude for February delivery also declined and last traded right above 110 dollars a barrel.