Iran will not abandon its right to nuclear technology, a former president and one of the country's most influential politicians has said.
Mr Rafsanjani said Iran had a right to nuclear power
Akbar Hashemi Rafsanjani told worshippers at Friday prayers in Tehran that foreign negotiators faced trouble unless they changed their approach.
His remarks come after the UN nuclear watchdog called for Iran to step up its co-operation with nuclear inspectors.
Iran says it wants nuclear power for peaceful purposes.
"I say to Europe, US and the [International Atomic Energy] agency (IAEA) that this style of confrontation will definitely not bring you a favourable result, and it will cause trouble for you," Mr Rafsanjani said.
He added that Iran "will certainly not refrain from its right to use peaceful nuclear energy".
European negotiators want Iran to abandon uranium enrichment in return for trade and security benefits.
The US has accused Iran of secretly trying to develop nuclear weapons - a charge Tehran denies.
However, Washington has suggested it is considering whether to back the EU initiative.
A high-level meeting of the IAEA ended in Vienna on Thursday with the board of governors calling on Iran to increase its transparency about its nuclear activities.
However, the governors expressed optimism about the outcome of talks between Tehran and Britain, France and Germany.