Iran - the second largest OPEC producer after Saudi Arabia - produces 3.7 million barrels of oil a day. After years of insufficient investment in infrastructure, however, that output is threatened. Iran's deputy oil minister, Mohsen Khojasteh-Mehr, says the country has to invest at least $32 billion to maintain its production capacity. If it does not do so, output will fall to 2.7 million barrels per day by 2015.