Global sanctions cut Iran's crude oil exports by 39% in 2012, to 1.5 million barrels a day, the lowest level since 1986, during the Iran-Iraq war, the U.S. Energy Information Administration said Friday.

Tighter restrictions on Iranian oil sales, led by the U.S. and the European Union, cut Iran's net oil export revenue by 27.4% in 2012 from a year earlier, to $69 billion, the EIA said. Based on earlier estimates from EIA that revenue figure would be the lowest for Iran since 2009, when oil prices were some 56% below the 2012 level.

EIA's assessment on Iran oil revenue and income cover crude oil and condensate, which is produced in association with natural gas and can be substituted for crude oil in some cases.

Sanctions on Iran took hold in 2011 and were tightened in 2012, and included an EU embargo on Iran's oil imports, over concerns that Iran's nuclear efforts went beyond Tehran's proclaimed efforts to establish a peaceful, nuclear-power program.

Iran's oil exports are estimated to make up 80% of Iran's total export earnings and 50% to 60% of government revenue, the EIA said, citing the Economist Intelligence Unit.