WASHINGTON, Oct 15 (Reuters) - The U.S. Senate on Thursday approved legislation to punish foreign oil companies that export gasoline to Iran, marking the first time both chambers of Congress have cleared the same bill imposing economic sanctions on Iran to protest its nuclear program.

The U.S. House of Representatives approved the same measure earlier this month to ban companies that sell Iran gasoline from also delivering crude oil to the U.S. emergency petroleum stockpile. The bill now goes to President Barack Obama, who is expected to sign it into law.

The sanctions on Iran's fuel suppliers were included in an energy and water programs spending bill. The measure would block the U.S. Energy Department from awarding contracts to companies to deliver oil to the U.S. Strategic Petroleum Reserve if the companies sell or ship gasoline to Iran.

The provision was sponsored by Senators Jon Kyl and Susan Collins.

"Time is running out for Iran to give up its illegal nuclear weapons program," the senators previously said about their proposed sanctions.

Congress and the Obama administration fear Iran's uranium enrichment program will be used to develop weapons, while Tehran says it is for peaceful purposes to generate electricity.

Congress hopes cutting off Iran's gasoline supplies will put pressure on Tehran to give up its nuclear program. While Iran holds some of the world's biggest oil reserves, it must import 40 percent of its gasoline to meet domestic demand.

However, the sanctions would limited impact as a deterrent as the the U.S. petroleum reserve is just 2 million barrels short of its 727-million-barrel capacity, which will be reached by January.

The emergency reserve was created by Congress in the mid-1970s after the Arab oil embargo. It holds crude in underground storage caverns at four sites in Texas and Louisiana.

Meanwhile the chairman of the House Foreign Affairs Committee said on Thursday his panel will vote Oct. 28 on separate legislation to expand a 1996 Iran sanctions law to effectively bar foreign companies that sell gasoline to Iran from doing business in the United States.

The legislation includes companies that provide ships or shipping services to transport the fuel, underwrite the shipments and finance or broker the gasoline cargoes.

Rep. Howard Berman said his committee "will take the first key step to ensure that President Obama is empowered with the full range of tools he needs to address the looming nuclear threat from Iran even as he pursues diplomacy and, if necessary, the multilateral sanctions track." (Editing by Christian Wiessner)