A recent agreement between four of Europe's largest oil companies and the U.S. aimed at further isolating Iran has left Iran Air, the Islamic republic's national carrier, unable to refuel its planes in most of Europe, the Washington Post reported.

Under the agreement, announced in Washington on Sept. 30, Total of France, Statoil of Norway, Eni of Italy, and Royal Dutch Shell of Britain and the Netherlands pledged to end their investments in Iran and avoid new activity in the country's energy sector. In turn, U.S. officials said, the companies would be protected from possible U.S. penalties for doing business with Iran.

As a result of the canceled jet fuel contracts, all Iran Air planes are now forced to make lengthy fuel stops in Germany or Austria, where Total of France and OMV of Austria are still providing jet fuel until their contracts run out, possibly as soon as next month.

Representatives for major oil firms say jet fuel sales to Iran Air are good business but too dangerous to pursue given the threat of sanctions by the United States. "All big oil companies are in daily contact with the U.S. State Department regarding Iran," said a representative of a major oil firm on the condition of anonymity because of the sensitivity of the subject. "Be sure that the Obama administration is fully aware of the situation Iran Air is in."

Read more in the Washington Post.