Iran's former President Mohammad Khatami has urged caution to avoid another UN resolution against Iran over its nuclear programme.
Mr Khatami has been criticised for not speaking out sooner
Mr Khatami has added his voice to fellow reformists who are questioning the direction of Iran's nuclear policy.
World powers are considering more punitive sanctions against Iran, which has failed to meet a UN deadline to halt its enrichment programme.
Iran insists its nuclear programme is solely for peaceful purposes.
Western nations say Tehran is hoping to develop a nuclear arsenal.
In a separate development, Russian officials said the launch of Iran's first nuclear power station would probably be delayed by two months.
Representatives of Atomstroiexport, the Russian state-owned company building the Bushehr plant, said lack of funds meant it would be completed in November instead of September this year.
No fuel deliveries would be made to the plant this year, they said.
In an interview with an Iranian newspaper, former Mr Khatami conceded that the outside world does have legitimate worries about Iran's nuclear programme that need reassuring.
He said Iran did not want a nuclear bomb but it should use patience and tolerance to remove the concerns of those who worry about the risks of proliferation.
Iran insists its nuclear programme is for peaceful purposes
Mr Khatami stressed Iran should insist on its right to nuclear technology, but he said courage should be shown to avoid a crisis, or at least minimise the damage.
"I believe we should pay a certain price, and pay it bravely, for talks and not head towards crisis as well as guaranteeing our rights in future," he said.
"We must try to prevent the adoption of another resolution."
His remarks came as Israeli Foreign Minister Tsipi Livni urged the international community to extend sanctions "without delay".
Speaking to a meeting of the American Israel Public Affairs Committee, she said sanctions imposed in December after Iran failed to stop uranium enrichment were already having an impact.
The BBC's Frances Harrison in Tehran says it is significant that a figure of such international standing as Mr Khatami has spoken out against the handling of the nuclear issue, but some reformists feel he should have done this sooner.
Mr Khatami's tone is the complete opposite of his successor, President Mahmoud Ahmadinejad, who recently compared Iran's nuclear programme to an unstoppable train with no brakes or reverse gears.
Reports say Mr Ahmadinejad now wants to address the UN to defend Iran's right to nuclear technology.
But he has been criticised inside Iran for using undiplomatic language that has damaged international relations.