The Obama administration has hit three energy companies with sanctions for providing large amounts of fuel to Iran.
The State Department says Chinese company Zhenrong brokered the delivery of more than $500 million in gasoline to Iran in a six-month period.
Singapore-based Kuo Oil sent $25 million in refined petroleum to Iran, and FAL Oil Co. Ltd. of the United Arab Emirates shipped more than $70 million in refined petroleum to the Islamic republic in late 2010.
The department says all three companies made individual transactions worth more than the $1 million allowable under U.S. law. Annual values cannot exceed $5 million.
The sanctions bar the companies from receiving U.S. export licenses.
The U.S. and its partners are trying to get Iran to halt its disputed nuclear program.