The US Defence Secretary has called for Iran to be given more time to respond to sanctions during a speech in Tunis.
Mr Panetta's remarks came a day before a much-publicised trip to Israel, where concern about Iran's nuclear ambitions is a high priority.
He admitted that sanctions against Tehran had not yet been successful, but said he believed more pressure on the Ahmadinejad regime would convince Iran to "do what's right."
Mr Panetta said that although it was not obvious, the sanctions were still having a "serious impact in terms of the economy in Iran"
He added: "What we all need to do is to continue the pressure on Iran, economically and diplomatically…to negotiate and to ultimately do what's right in joining the international family."
However he did state that "all options" remained on the table against Iran, if the sanctions did not work.