The Senate voted 76-22 for the non-binding amendment sponsored by Republican Jon Kyl and independent Joseph Lieberman to place the Iranian Revolutionary Guard Corps, or Pasdaran, on the US terrorist blacklist.
Such a designation if adopted by the US government would open the corps and affiliated companies to economic sanctions.
US military officials and lawmakers have accused the Revolutionary Guard of arming Shiite militias in Iraq, and supplying sophisticated roadside bombs used to kill US soldiers in the war-torn nation.
The US administration also accuses Iran of seeking to build an atomic bomb under the cover of a civilian nuclear program, a charge Tehran denies.
The Bush administration said in August it would designate all or part of the Guard as a terrorist organization.
The blacklist, which already includes Al-Qaeda and Hezbollah, bars named groups from gaining access to the US financial system.
The House of Representatives adopted a similar text on Tuesday against the backdrop of rising tensions between Iran and the United States and a scathing attack on the United States by Iran’s hardline president, Mahmoud Ahmadinejad, before the UN General Assembly.
The House bill also calls for penalizing foreign companies with US subsidiaries which invest in Iran, particularly in the oil and gas sector.
Iran has been on the US government state sponsors of terrorism blacklist for more than two decades.
Already this year, the US government escalated financial sanctions against Tehran.
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.