A measure targeting the elite military corps and the lucrative Iranian energy sector sailed through the House by 397 votes to 16, hours before Ahmadinejad’s speech to the United Nations General Assembly.
The legislation is aimed at depriving Iran of proceeds from energy sales which could be diverted into funding its nuclear program, which the West says is intended to produce atomic weapons, a charge Tehran denies.
Its top sponsor, veteran Democratic chairman of the House Foreign Affairs committee, Tom Lantos, said the bill was needed because Iran’s denials of a nuclear weapons program could not be believed.
"I wish that we could take Ahmadinejad at his word, but we obviously cannot," Lantos said.
"This is the same man who yesterday said, ‘Our people are the freest in the world, and there are no homosexuals in Iran.’"
Ileana Ros-Lehtinen, the committee’s top Republican, added: "Too many foreign energy firms have become functional allies in Tehran’s efforts to build a nuclear bomb."
The bill sanctions foreign companies with US subsidiaries which invest in Iran, particularly in the oil and gas sectors.
It also prohibits civilian nuclear cooperation with nations that support Iran’s nuclear program and calls on the US government to urge foreign states and banks to divest from Iranian interests.
The bill passed as six key world powers working to curb Iran’s nuclear activities scheduled new talks on imposing new sanctions against the Islamic state.
It also calls on the State Department to designate the Islamic Revolutionary Guard as a "foreign terrorist organization" and therefore open the corps and affiliated companies to economic sanctions.
US military officials and lawmakers have accused the Guards of arming Shiite militias in Iraq, and supplying sophisticated roadside bombs that kill US soldiers in the war-torn nation.
The Bush administration said in August it would designate all or part of the Guards as a terrorist organization.
Iran has already been on the US government state sponsors of terrorism blacklist for more than two decades.
The Senate was expected to vote on a bill as early as Tuesday also calling for the Guards to be blacklisted as a terrorist group.
The House bill, named the Iran Counterproliferation Act, takes away the often used power of the US president to waive sanctions against giant global oil firms which do business in the Iranian energy sector.
It also bars Iranian imports into the United States.
Already this year, the US government has escalated financial sanctions against Iran.
The US Treasury and other government agencies have blacklisted and applied asset freezes against at least 15 Iranian entities.
Most, including the Atomic Energy Organization and the Mesbah Energy Company, operate in the nuclear, energy and industrial industries.
Iran’s banking sector is also in Washington’s sights, as well as Iranian groups it says fund "terrorist" organizations such as Hezbollah, the Lebanese-based Shiite political and militant group.
The Treasury blacklisted Iran’s fifth-largest state-owned bank, Bank Sepah, in January, claiming it had funded weapons proliferation, including a Chinese firm’s sale of "missile-related items" to Iran in 2005.
In July, the House passed a bill requiring the naming of foreign companies with more than 20 million dollars in Iran’s energy sector, paving the way for US federal and state pension funds to divest from such firms.
The Guards is fiercely committed to defending the ideals of Iran’s revolutionary founder Ayatollah Ruhollah Khomeini.
Ahmadinejad fought for the Guards during the 1980-1988 war with Iraq.