When presented with the details Tuesday, Iran said the package contains "positive steps" but also ambiguities, which it said had to be cleared up in further talks. It said it would study the package before announcing its stance.

EU foreign policy chief Javier Solana, who conveyed the offer to Tehran, said he expected a reply within "weeks."

Iran has consistently refused to give up enrichment, a process that can produce either fuel for a nuclear reactor or the material for a nuclear warhead. Iran insists its program is peaceful and that it has the right to develop enrichment -- though it has signaled it might compromise on large-scale enrichment.

On Friday, a powerful hard-line cleric, Ayatollah Ahmad Jannati, came out against the Western incentive package, reflecting conservative pressure on the government to reject the offer.

"It's not good for Iran," Jannati said in his Friday prayer sermon, telling worshippers that the West has "no choice but to accept" an Iranian enrichment program.

Jannati is the head of the powerful Guardian Council, a constitutional watchdog arbitrating between the parliament and the government. He holds considerable influence, but the ultimate power in state matters lies with supreme leader Ayatollah Ali Khamenei, who has sometimes overruled hard-liners on the nuclear issue.