"The era of threats and political pressure is over and we believe in resolving issues through dialogue and interaction," government spokesman Gholam Hossein Elham told reporters.

"What we are talking about is a real change in their behaviour and they should change their domineering methods," he added.

In testimony to Congress on Wednesday, Clinton said Washington supported efforts by world powers to resolve the Iranian nuclear issue diplomatically.

"But we are also laying the groundwork for the kind of very tough, I think you said crippling, sanctions that might be necessary in the event that our offers are either rejected or the process is inconclusive or unsuccessful."

On Friday, Iran's influential former president Akbar Hashemi Rafsanjani warned Clinton that she risked undermining the new prospects for dialogue between Tehran and Washington.

"Clinton says 'we are ready for talks but beside that we prepare for paralysing sanctions against Iran'," Rafsanjani said.

"What can they expect of us when such things are said?... They'd better not repeat these comments so the atmosphere existing in Iran today for talks is not ruined."

Clinton's comments came the same day that chief nuclear negotiator Said Jalili said that Iran was ready for a ""constructive dialogue" with world powers.

The five veto-wielding permanent members of the UN Security Council -- Britain, China, France, Russia and the United States -- plus Germany have been seeking to persuade Iran to accept a package of political and economic incentives in return for ending its efforts to master the nuclear fuel cycle.

Western governments fear that Iran's nuclear programme is cover for a drive for a bomb, something Tehran strongly denies.

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