Iran Sanctions Enhancement Act of 2007
The Iran Sanctions Enhancement Act of 2007, introduced in the United States House of Representatives by Representative Mark Kirk, Republican-Illinois, and Representative Rob Andrews, Democrat-New Jersey, would threaten sanctions against any company or individual that provides Iran with refined petroleum products or engages in an activity that could contribute to the enhancement of Iran's ability to import refined products after December 31. The bill could potentially lead to sanctions against gasoline brokers, tankers and insurers. US companies are prohibited from trade with Iran under unilateral sanctions, but most foreign companies are free to trade with Tehran.
The United States, which is leading efforts to isolate Iran over its nuclear plans, has said Iran's gasoline imports are a point of "leverage." Washington accuses Iran of seeking to build nuclear weapons, a charge Tehran denies.
According to Mark Kirk, Americans were studying around this plan over the last five years. 
Unlike other US sanctions programs, foreign subsidiary companies of US companies are not restricted from doing business with Iran, even to the extent of supplying US-origin goods to Iran.