The panel, led by Democratic Senator Christopher Dodd, voted 23-0 to pass the legislation, which notably targets firms that help the Islamic republic obtain refined petroleum products like gasoline.

The vote came as the US State Department said Washington awaited a "formal response" from Tehran to a UN-brokered plan on nuclear cooperation with major powers.

"We must send a clear signal to Iran's leaders that, if they continue to defy the will of the international community, our nation is prepared to confront them on that," Dodd said in a statement.

Oil-rich Iran, which denies the West's charges that it seeks to develop nuclear weapons, lacks refining capability and relies on imports to satisfy 40 percent of its thirst for gasoline.

US lawmakers, including President Barack Obama's Democratic allies, have shown a growing willingness to seek sanctions against Iran even as they watch for the results of nuclear talks between Tehran and world powers.

On Wednesday, the House Foreign Affairs Committee approved legislation enabling Obama to slap sanctions on firms involved in shipping refined petroleum products to Iran or helping the country's domestic refining efforts.

The Senate measure groups several measures being discussed in the House of Representatives, all portrayed by their supporters as giving Obama new clout in the difficult nuclear negotiations.

The banking committee's legislation would notably close US markets to Iranian carpets, caviar, and pistachio nuts -- which then-president Bill Clinton exempted from a US trade embargo in an olive branch to Tehran.

It also requires that the president report to congress when non-US companies become eligible for sanctions, under a 1996 law that punishes investments of more than 20 million dollars in Iran's energy sector.

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 measure also expands the 1996 law to cover oil and gas pipelines and tankers, and requires the administration to freeze the assets of any Iranians, including members of Iran's Revolutionary Guard Corps, found to be active in weapons proliferation or terrorism.

It would also enable US investors, including states' pension funds, to divest from energy firms that do business with Iran.

It would prohibit the US government from purchasing goods from firms that do business in Iran's energy sector, or provide sensitive communications technology to Iran -- a measure that could affect telecommunications giants Siemens and Nokia.

The legislation's ultimate fate is unclear: Both the full Senate and House of Representatives must approve the same bill in order to send it to Obama to sign into law.

And US presidents have used a national security waived built into the original 1996 sanctions bill to avoid imposing sanctions on Iran.

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