"This week's negotiations with the Europeans are the most important part of the nuclear negotiations," Iran's vice president and atomic energy head Gholamreza Aghazadeh told state television.

"The conclusion of three months of nuclear negotiations is close, and the Europeans this week should more clearly tell us their plans," he added. "We are expecting the negotiations to be serious and meaningful."

Iran agreed in November with Britain, France and Germany to suspend all uranium enrichment-related activities in order to ally fears of a weapons drive and in return for talks on trade, security and technological incentives.

The Iran-EU talks began in Brussels in December, moved to Geneva in January and are to resume this week in Geneva.

But there is a risk of deadlock, with EU negotiators demanding Iran totally dismantle its nuclear fuel programme, including enrichment, to provide the necessary "objective guarantees" that it does not seek atomic weapons.

Sirus Naseri, a member of Iran's nuclear negotiations strategy committee, said Tehran would not bow to such a demand.

Enrichment is a key process that can make fuel for nuclear reactors as well as the explosive core of an atomic bomb.

Provided the purpose is peaceful, the fuel cycle is authorised by the nuclear Non-Proliferation Treaty (NPT) -- a right that Iran stands by but critics see as a dangerous loophole in the treaty.

"This proposal will not go anywhere," Naseri said of wider calls -- notably from Mohammed ElBaradei, the International Atomic Energy Agency (IAEA) head -- for a revision of the NPT that would deny widespread access to the fuel cycle.

He told state television that Iran had already "reached the point of no return in the fuel technology issue.

"The proposal will definitely fail ... a monopoly in the field of energy is something unbelieveable," Naseri added.

According to government spokesman Abdollah Ramazanzadeh, "the issue with the Europeans is negotiating a timetable for the resumption of nuclear activities for peaceful purposes.

"We have not reached a conclusion yet, we are expecting the positions of both sides to be stated more clearly. We will not allow these negotiations to go on for a long time," he told a news conference.

And powerful former president Akbar Hashemi Rafsanjani told USA Today newspaper that he was "not satisfied with the progress" of the negotiations, "but I am happy that the talks are going on."

On Sunday, US Vice President Dick Cheney said the United States backs the European diplomatic effort but has not "eliminated any alternative."

"I think there's a good-faith effort underway by our European allies to try to resolve this issue diplomatically. We support that effort," the vice president said in an interview with Fox News.

"There are a number of steps here to be considered. We have not eliminated any alternative at this point, but we obviously are seriously pursuing diplomatic resolution of this problem," Cheney said.

Washington has not ruled out using military force against Tehran although US Secretary of State Condoleezza Rice said last week that that "the question is simply not on the agenda at this point."

The IAEA, which has been investigating Iran for two years, has found plenty of evidence pointing to suspicious activity but no "smoking gun" that proves Iran is seeking the bomb.

Iran insists it only wants to be self-sufficient in nuclear energy, and free up its vast oil and gas reserves for export.

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