Foreign Minister Mohammad Javad Zarif said Iran would approach crunch nuclear talks in Geneva next week "with good faith" and "with determination to reach understanding and with hope to reach an understanding at an early stage".
A decade of on-again-off-again talks with global powers restarted in mid-October, amid a thaw in relations brought about by the election of perceived moderate president, Hassan Rouhani.
At the time Iranian negotiators expressed hope a deal could be reached "within a year".
Tehran insists its nuclear technology is solely for peaceful purposes. But it has resisted demands by the UN Security Council permanent members (the United States, Russia, China, France and Britain) for extensive monitoring and the curbing of contentious activities.
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Zarif said today it was possible to overcome years of fraught relations.
"Of course overcoming several years of a build-up of mutual lack of confidence requires time to overcome and requires time to heal," he said after a bilateral meeting in Pretoria.
"We believe that even a perception that Iran is seeking nuclear weapons is detrimental to our security so we will do our best in order to remove that perception."
He insisted, however, that the global powers must respect Iran's right to develop civilian nuclear power, including the ability to enrich nuclear materials.
Iran and the so-called P5+1 group -- the UN Security Council permanent members plus Germany -- are due to meet again in Geneva on November 7-8.