BBC: US Secretary of State Hillary Clinton says the US has been discussing with partners ways of putting pressure on Iran to ends its nuclear programme. BBC News
US Secretary of State Hillary Clinton says the US has been discussing with partners ways of putting pressure on Iran to ends its nuclear programme.
But the White House said the "door is still open" for Iran to return to talks over nuclear enrichment.
Iran is already subject to three sets of UN sanctions for refusing to suspend its uranium enrichment programme.
US President Barack Obama had said harsher steps would be taken if Iran failed to respond by the end of 2009.
Mrs Clinton said the US had begun speaking to its partners and "like-minded nations" about pressure and sanctions.
She said the goal of the US was to "pressure the Iranian government, particularly the Revolutionary Guard elements, without contributing to the suffering of the ordinary [people], who deserve better than what they currently are receiving."
White House spokesman Bill Burton said the door was "still open for Iran to take the right decision and respect its international obligations".
"We are going to take the necessary steps to encourage them to return to the table," he said.
"We'll be going through the appropriate process to try to get them to the table and do exactly what they're supposed to do."
Iran says its nuclear programme is for purely peaceful purposes but many in the West fear it is developing weaponry.
Tehran has rejected a plan put forward by the UN's nuclear watchdog, the International Atomic Energy Agency (IAEA), under which Iran would have sent most of its uranium abroad for further enriching.
Mr Obama's administration had set an end-of-year deadline for serious progress towards a comprehensive solution.