Washington: The Bush administration rolled out an unprecedented package of unilateral sanctions against Iran yesterday.

It also designated the Revolutionary Guard Corps a proliferator of weapons of mass destruction and the elite Quds Force for supporting terrorism, according to senior administration officials.

The package, announced jointly by Secretary of State Condoleezza Rice and Treasury Secretary Henry M. Paulson Jr, marks the first time that the United States has tried to isolate or punish another country's military. It is the broadest set of punitive measures imposed on Tehran since the 1979 takeover of the US Embassy, the officials said.

"This is a very powerful set of measures designed to send a message to Iran that there will be a cost to what they do. We decided on them because we have seen no change in Iranian behaviour," said a senior administration official who spoke on the condition of anonymity. "Our diplomacy needs to be stronger and more effective."

The move caps a year of growing US pressure on Tehran, including billions of dollars in arms sales to its Gulf allies and Israel, interception of Iranian arms shipments in Iraq and Afghanistan, detention of Iranian agents in Iraq, and pressure on the United Nations and European allies to increase Iran's isolation. The dramatic US steps underscore the escalating tensions between the US and Iran.

"The policies of Iran constitute perhaps the single greatest challenge for American security interests in the Middle East, and possibly around the world, because the combination of Iranian terrorism, Iranian repression at home and the pursuit of nuclear weapons technology - technologies that could lead to a nuclear weapon - is a very dangerous mix," Rice said on Wednesday in testimony before the House Foreign Affairs Committee.

The new sanctions empower the United States to financially isolate a large part of Iran's military and anyone inside or outside Iran who does business with it, US officials said. The measures could affect hundreds of foreign companies by squeezing them to drop Iranian business or risk US sanctions.

The Revolutionary Guard Corps, which numbers at least 125,000, is the most powerful wing of Iran's military. It controls a growing sector of the economy, including construction companies, aspects of the oil industry, pharmaceutical plants, telecommunications and ordinary commerce. US officials said it also operates the front companies that procure nuclear technology.

The administration designated the entire Revolutionary Guard under Executive Order 13382, signed by President Bush in June 2005, which allows the United States to freeze the assets of any proliferator of weapons of mass destruction and its supporters. Iran is being designated for its ballistic missile programme.

The Quds Force, the foreign operations branch of the Revolutionary Guard Corps, was designated separately as a supporter of terrorism under Executive Order 13224, which Bush signed two weeks after the September 11, 2001, attacks to obstruct terrorist funding, US officials said.

"The Quds Force controls the policy for Iraq," Gen David Petraeus, the top US commander in Iraq, said earlier this month.