After the decision of the international community to lift the economic sanctions against Iran, which was achieved mainly with American initiatives, Iran is back to the international economy and wants to be paid in euros and not dollars for the oil it is going to export. See Reuters “Iran wants euro payment for new and outstanding oil sales”, February 2016.
As you can read in the article, all these years Iran has been asking the other members of the international oil cartel (OPEC) to dumb the dollar and get paid in euros for their oil exports, but the other countries did not agree. And still it was the United States that played the major role in bringing Iran back to the international economy.
That’s very important because many silly people who read communist and nazi propaganda believe that the Arab Spring happened because Muammar Qaddafi, the Libyan dictator, wanted to sell oil in euros and not in dollars and other similar nonsense. Countries want to get paid in dollars and euros for the same reasons you prefer to get paid in dollars and euros rather than in some other currencies. And note that Iran has almost 160 billion barrels of oil while Libya has only 50 billion.
For the Reuters article see:
“Iran wants euro payment for new and outstanding oil sales”, February 2016