A powerful Iranian cleric said on Friday a package of incentives offered by six major powers would never stop Iran making nuclear fuel.

The United States, Britain, France, Germany, Russia and China have presented Tehran with proposals they hope will persuade it to halt uranium enrichment, a process the West fears Iran will use to build atomic weapons.

"Now they want to deprive us of many advantages. The package they have brought is a package that is good for themselves and is not appropriate for the Iranian people," Ayatollah Ahmad Jannati told worshippers at Friday prayers in Tehran.

Jannati heads the Guardian Council, Iran's highest constitutional watchdog.

The council does not directly make nuclear policy. Supreme Leader Ayatollah Ali Khamenei has entrusted the handling of nuclear affairs to the Supreme National Security Council.

"In short, we must have enrichment to the level of 3.5 to five percent and they have no choice but to accept it," Jannati added.

Iran says it needs uranium enriched to this low level to fuel power stations and has no intention of enriching uranium to the higher level needed for weapons.

It has failed to convince the international community and has been referred to the U.N. Security Council for possible sanctions.

Analysts see the package of proposals as an attempt to give Tehran a last chance before pulling together a united front for action against Iran at the world body.

The package offered to Iran has not been made public, but Western diplomats say it includes a U.S. pledge to join European-led talks and offers of a light-water reactor and a facility to stockpile nuclear fuel.

Iranian officials have said they are willing to consider the proposals but have reiterated that they can never back down on making nuclear fuel themselves. Without this concession, the proposals cannot succeed.