BBC: Iran has responded defiantly to new sanctions imposed by the US targeting Iran's Islamic Revolution Guards Corps and three state-owned banks.
The Iranian foreign ministry said the sanctions were doomed to failure.
US Secretary of State Condoleezza Rice says the measures are to "confront the threatening behaviour of the Iranians".
But both China and Russia criticised the sanctions. Russian President Vladimir Putin likened the US move to "mad people wielding razor blades".
Earlier, US Assistant Secretary of State Nicholas Burns criticised Russia for selling weapons to Iran and China for investing in the country.
He told the BBC: "It's very difficult for countries to say we're striking out on our own when they've got their own policies on the military side, aiding and abetting the Iranian government in strengthening its own military." Iran defiant at new US sanctions (more)
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Iran and the US: A new Cold War? By Roger Hardy
Mark Alexander
