"We need a common position of all European Union member states," Energy Commissioner Guenther Oettinger said when asked about a possible ban.
Oettinger, on a visit to Moscow, added that he had not held any talks with oil exporter Russia or other members of the Organisation of the Petroleum Exporting Countries (OPEC) to make up any shortfall if Iran is taken out of the European market.
Oettinger did not elaborate, but his comments suggested that an effective oil embargo, backed by all 27 EU member states, may not be workable.
EU members take 450,000 barrels per day of Iranian oil, some 18 percent of the country's exports.
EU foreign ministers were meeting in Brussels on Thursday to discuss tougher economic sanctions against Iran after a report by the UN atomic energy watchdog concluded that Tehran has worked on designing an atom bomb.
Tensions have escalated this week over the storming of the British embassy in Tehran by protesters, which has led Britain to pull out its diplomatic staff and shut the Iranian embassy in London.
France, Germany and the Netherlands have also recalled their envoys to Tehran.
French President Nicolas Sarkozy had proposed the oil import ban and won backing from Britain, but resistance from other countries such as Greece, facing an economic slump and huge debt burdens, persists.
