Sanctions on Iran caused the Islamic Republic’s oil revenue  to drop by $40 billion in 2012, according to The International Energy Agency .
In its monthly oil report , the IEA said that output from the country have dropped to 2.65 million barrels per day in January, down from a high of 3.7 mpd before western sanctions were imposed.
The newly released figures come as the International Atomic Energy Agency arrives in Tehran for a fresh round of talks.
"Iranian crude oil production continued to edge lower in January and may fall further in coming months following implementation on February 6 of additional sanctions by the US, the agency said in its month report, according to AFP.
Western countries have put economic sanctions on Tehran  over its alleged nuclear programme, which the West believe is being used to create a nuclear weapon. Iran denies this, saying it is purely for peaceful purposes.