The U.S. Energy Department's Energy Information Administration said that, while global oil supply in 2012 increased 1.8 million barrels per day, Iran's oil production fell 700,000 bpd from the previous year.
"Most of the 2012 drop in production is attributable to tightened sanctions," the EIA reports. "A smaller decline in 2011 resulted mainly from declining production in aging fields."
U.S. and European sanctions targeting Iran's energy sector are meant to limit revenue that could be used to finance Tehran's nuclear program, which Iran says is for peaceful purposes.
The EIA said oil exports accounted for about 60 percent of its federal revenue. Oil export revenue in 2012 was estimated at $69 billion, down more than 30 percent from the previous year.
For existing consumers, the EIA said refiners in South Korea and India may suffer the most because of European restrictions on insurance for crude oil shippers. "The new sanctions may further affect Iran's exports and production over the next few months as refiners try to find alternative suppliers of insurance," the EIA stated.
Some countries are eligible for waivers from U.S. sanctions if they can show they've "significantly" cut back on Iranian crude oil deliveries.
The EIA said Iran is the second-largest crude oil producer among the Organization of Petroleum Exporting Countries. OPEC ranks Iran behind Venezuela and Saudi Arabia in total estimated reserves.