Top Republican members of the House of Representatives said the Islamic republic was exploiting President Barack Obama's policy of engagement to pursue what the West charges is a covert atomic weapons quest.
"The time is now for Congress to enact the strongest possible sanctions against the regime in Iran," said Representative Mike Pence, the number three Republican in the House.
Pence linked the move to the pending visit of Iranian President Mahmoud Ahamdinejad to the UN General Assembly next week and said Obama's Democratic allies, who control the congress, must act on the bill this week.
The Iran Refined Petroleum Sanctions Act, introduced in late April, would effectively bar any non-US firm that sells refined petroleum to Iran, or facilitates such sales, from doing business in the United States.
Because of a lack of domestic refining capacity, oil-rich Iran is dependent on gasoline imports to meet about 40 percent of domestic consumption.
Iran gets most of its gasoline imports from the Swiss firm Vitol, the Swiss/Dutch firm Trafigura, France's Total, the Swiss firm Glencore and British Petroleum, as well as the Indian firm Reliance.
The legislation has some 300 co-sponsors in the House of Representatives and broad support in the US Senate.
Democratic Representative Howard Berman, the bill's lead author and chairman of the House Foreign Affairs Committee, has said he will give Obama's approach time and wait until the end of September to see whether Iran bows to global pressure to freeze its uranium enrichment program.
"Where is the sense of urgency? Simply put: There is none," charged Representative Ileana Ros-Lehtinen, the top Republican on Berman's committee.
"We should do everything we can to up the pressure on that regime in order to at least present a likelihood of producing results," said Representative Eric Cantor, the number two Republican in the House.
