WASHINGTON: The leaders of a bipartisan panel in the U.S. House of Representatives is proposing legislation designed to reduce Iran's import of gasoline.

The move by Reps. Mark S. Kirk, a Republican, and Robert E. Andrews, a Democrat, who set up a congressional working group on Iran's nuclear programs two years ago, coincided with angry protests in Tehran against fuel rationing.

While Iran is one of the world's largest oil producers, a lack of refineries compels the Islamic government to import nearly half the gasoline used by Iranians.

Besides the rationing, which sparked street demonstrations in Tehran and criticism of Iranian President Mahmoud Ahmadinejad, the government boosted gasoline prices last month.

Under the proposed legislation, any company that provided Iran with gasoline or helped it import gasoline after the end of the year could lose its access to American customers through sanctions.

"This is becoming the critical weakness of the Iranian government, meaning its dependence on gasoline," Kirk said in a telephone interview. "The riots show the gasoline shortage is a growing danger to the Iranian regime and a diplomatic opportunity for Western countries to force Iran to adhere to international nuclear rules."

Most of Iran's gasoline imports come from Gulf states and India brokered by the Dutch trading house Vitol. Most of the gasoline tankers are insured by Lloyds of London.

The bill would give President George W. Bush the option of deciding which of several penalties to impose. These would include denial of loans and credits from the U.S. Export-Import bank as well as loans or licenses for exports to the United States.

Andrews said in an interview that success depends on whether the U.N. Security Council eventually punishes Iran with another resolution.

"If we don't have international cooperation, the embargo won't be effective," Andrews said. He predicted that if Iran faced a choice between a gasoline embargo and giving up its nuclear program, it would abandon the program.

On Tuesday, the House Foreign Affairs Committee approved legislation designed to strike at investments in Iran.

The bill, championed by the committee chairman, Democratic Rep. Tom Lantos, would end the Bush administration's power to waive sanctions against foreign companies that invest in Iran.

"Our goal must be zero foreign investment," Lantos said.

A State Department spokesman, Tom Casey, agreed Thursday that "we need to do everything that we can to continue to raise the stakes in Iran in terms of its nuclear program."

He said the United States was working with friends and allies in Europe and elsewhere gradually to ratchet up sanctions against Iran.

"We are in the process now of looking at what additional measures we can add," Casey said.

However, the spokesman also said the administration had to move carefully in order to hold together "the broad international coalition that we've worked to build."

Several countries that do lucrative business with Iran have balked at applying severe pressure on the Tehran government.

Among the arguments the Bush administration has with Iran is its nuclear program. The United States and its European allies are convinced Iran is trying to build nuclear weapons. Iran insists its program is aimed at developing civilian energy.