The European Council last month approved of an embargo on Iranian oil, a measure that will enter into force starting July 1. Member states, however, aren't allowed to enter into new fuel contracts with Tehran.
Catherine Ashton, Europe's foreign policy chief, said that while European imports account for only 20 percent of all of Iran's oil exports, Tehran relies on oil exports for 70 percent of its revenue.
"We are strongly increasing the pressure on Iranian government whilst avoiding as far as we possibly can negative effects on Iranian population," she said in a statement.
The managing director of the National Iranian Oil Co. told the Iranian Oil Ministry's information network that Tehran was ready to cut oil sales to Europe before July 1. The official said Iran would have "no problem" with finding non-European consumers for its crude oil.
Tarja Cronberg, a European lawmaker in charge of the delegation for relations with Iran, told the European Parliament's news service that European sanctions on Iran were rather broad.
"This will have an impact on the whole Iranian economy but whether it will make the government change its policy, we don't know," she said. "Probably not."
Sanctions were imposed to persuade Iran to abandon its nuclear ambitions. Many countries say they believe Iran is working to produce a nuclear bomb, an allegation Tehran denies.