The following article tells how Iran is not cooperating with the International Atomic Energy Agency and so sanctions against Iran are being proposed. The following article wonders if Iran will retaliate by stopping her oil exports to the West.

While that may cut our oil import, the real problem is the stranglehold Iran could put on the entire Persian Gulf and its exportation of oil by its Arab neighbors, should war break out in the MidEast. Actually, Iran is already in a confrontational posture and could bring that about over any incident.

"Iran will likely retaliate against the United States and its allies if any punishment is demanded by the Security Council. We should be clear about that. Very likely Iran will quit selling oil to the West, " ....
Iran could attempt to close the Straits of Hormuz through which moves most of the oil extracted from the Persian Gulf region."
http://www.sptimes.com/2006/09/12/Opinion/Sanctions_on_Iran_can.shtml