NEW YORK - Oil prices on Friday plummeted to below $30 a barrel as the expected increase in Iranian crude exports added to oversupply concerns.

Global oil prices are hovering near 12-year lows as the market braces for a surge of Iranian oil exports once international sanctions are lifted, possibly within days.

The Organization of the Petroleum Exporting Countries (OPEC) decided on against cutting output last December. The cartel's output is accounted for around 40 percent of the global crude output.

Iran, a member of OPEC, said it is looking to add about 500,000 barrels within weeks of the sanction relief.

Thanks to the US shale oil revolution, American oil production has almost doubled in the past six years. There is no sign that US shale oil producers started to cut production in face of the plunging prices.

The West Texas Intermediate for February delivery moved down $1.78 to settle at $29.42 a barrel on the New York Mercantile Exchange, while Brent crude for February delivery decreased 2.09 dollars to close at 28.94 dollars a barrel on the London ICE Futures Exchange.