"Iran does not trade its rights in return for incentives," government spokesman Gholam Hossein Elham told reporters.

"It is not reasonable to replace the (International Atomic Energy) Agency with some countries which themselves possess nuclear weapons," he said.

The UN Security Council last month tightened sanctions on Iran for failing to heed repeated ultimatums to suspend uranium enrichment.

The council's five veto-wielding permanent members -- Britain, China, France, Russia and the United States -- plus Germany have pledged to expand a 2006 offer of economic incentives to Iran in return for a freeze on uranium enrichment.

But Iran last month ruled out further talks with the six saying that concerns about its nuclear programme should be dealt with exclusively by the UN nuclear watchdog, the IAEA.

Iranian President Mahmoud Ahmadinejad said on Friday that he would reject any new incentives offered by world powers in return for suspending uranium enrichment.

"This is a non-negotiable subject," Ahmadinejad was quoted as telling Japan's Kyodo News.