The "Iran Diplomatic Enhancement Act" aims to punish entities that supply, broker, insure or deliver gasoline to Iran, or helps the Islamic republic build refineries domestically.

"If we are serious about stopping the emergence of a nuclear Iran, our window for effective diplomacy is starting to close," Republican Representative Mark Kirk, a main author of the bill, said in a statement.

"Iran's need to import a significant portion of its gasoline is among the best levers we have at our disposal," said Democratic Representative Brad Sherman, co-author of the legislation.

The lawmakers noted that Iran, though rich in oil, is estimated to rely on gasoline imports to meet 40 percent of domestic demand, most of it coming from five European firms and one Indian company.

Entities potentially affected include the Swiss firm Vitol, the Swiss/Dutch firm Trafigura, the French firm Total, the Swiss firm Glencore, and British Petroleum, as well as the Indian firm Reliance, while Lloyds of London insures the majority of tankers carrying gasoline to Iran, the lawmakers said.

The statement from Kirk and Sherman underscored that US President Barack Obama, during his 2008 White House run, had raised the prospect of trying to curb Iran's gasoline imports in response to Tehran's nuclear defiance.

"If we can prevent them from importing the gasoline they need and the refined petroleum products they need, that starts changing their cost-benefit analysis. That starts putting the squeeze on them," Obama said in October.

The new legislation would expand the criteria under which a company could face US sanctions under a 1996 law targeting investments over more than 20 million dollars in Iran's oil and gas infrastructure.

That measure listed possible sanctions like denial of US Export-Import Bank assistance, denial of export licenses, curbs on loans from US financial institutions, or restrictions on US imports from the affected company.

All rights reserved. � 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.