Oil giant Royal Dutch Shell says it is no longer selling gasoline to Iran, the latest in a growing number of oil firms to halt supplies to the Islamic Republic.
The Netherlands-based oil company announced the move Wednesday.
Other large Western firms that have stopped fuel sales to Tehran include Switzerland's Glencore and Geneva-based Vitol. Executives and traders say oil companies are moving away from Iran for political reasons.
U.S. lawmakers are working on legislation that backs unilateral sanctions on companies that make fuel deals with Iran. Lawmakers hope the sanctions will persuade Iran to stop expanding its nuclear program.
Iran is one of the world's largest oil exporters but still relies on imports for about 40 percent of its refined product. This dependence is largely due to decades of sanctions that have hindered Iran's refining capacity.
Iran spends billions of dollars each year on oil imports and energy subsidies for citizens.
Earlier this week, Iranian lawmakers blocked President Mahmoud Ahmadinejad's plans to cut energy and food subsidies by approving only half of the savings requested by his government.
Iranian media reported Tuesday that Mr. Ahmadinejad had called for subsidy cuts of $40 billion. Lawmakers, fearing that cuts in subsidies could cause inflation, agreed to save only $20 billion.
Some information for this report was provided by AFP, AP and Reuters.