WASHINGTON -- The Bush administration announced sweeping new sanctions against Iran on Thursday -- the harshest since the takeover of the U.S. Embassy in 1979 -- charging anew that Tehran supports terrorism in the Middle East, exports missiles and is engaging in a nuclear buildup.

U.S. Secretary of State Condoleezza Rice, joined at a State Department news conference by U.S. Treasury Secretary Henry Paulson, said the steps the administration of U.S. President George W. Bush is taking against the Revolutionary Guard Corps and a number of banks are designed, among other things, to punish Tehran for its support of terrorist organizations in Iraq and the Middle East.

The sanctions will cut off more than 20 Iranian entities, including individuals and companies owned or controlled by the Revolutionary Guards, from the U.S. financial system and will likely have ripple effects throughout the international banking community.

The Quds Force, a part of the corps that Washington accuses of provided weapons to insurgents in Iraq, will be identified as a "specially designated global terrorist" group for its activities in Afghanistan, Iraq and the Middle East, the officials said.

Rice said the new sanctions would "provide a powerful deterrent" for companies in the United States and abroad to sever business relationships with Iran.

Paulson said Iran channeled millions of dollars per year to help fund terrorist activities.