Iran sanctions: What you need to know
3 January 2012 Last updated at 18:57 GMT
Fresh sanctions have been announced by the United States against Iran, cutting off from the US financial system any foreign firms that do business with the Iranian central bank.
International pressure on Iran over its nuclear programme had already been stepped up in December, with the EU also agreeing to tighten its sanctions against the country.
BBC Persian's Amir Paivar explains the extent, importance and impact of the measures against Tehran.