The world´s six leading powers will try to defuse their nuclear- tipped confrontation with Iran on Monday when talks open in Moscow on the eve of Tehran suffering a total European Union oil embargo.

This measure, due to come into full effect on July 1, will cost Iran billions of dollars by banning any EU member state from importing the country´s oil. By maximising the economic pressure on Tehran, the aim is to break the impasse over its nuclear ambitions.

If Monday´s talks break down, however, the chances of the confrontation being resolved by diplomacy will greatly recede.

When the negotiations begin with Iran in the Russian foreign ministry in Moscow, a vital question will be at issue. The world powers have proposed that Iran stop enriching uranium to 20 per cent purity, hand over its stockpile of this material and close down a formerly secret nuclear facility at Fordow.

This demand comes from the "P5 plus 1", consisting of the five permanent members of the Security Council – America, Britain, France, Russia and China – along with Germany. In return, they would relax some of the more minor sanctions on Iran.

But Hossein Mousavian, who served as served as an Iranian negotiator on nuclear issues between 2003 and 2005, described this offer as "diamonds for peanuts" and predicted that Tehran would say no when the talks begin. "This is not something great to offer Iran," he said.

ran, for its part, is expected to demand formal recognition of its right to enrich uranium and the lifting of a wide range of sanctions before it will consider any steps of its own.

"We are ready on a voluntary basis to make a positive step if the other party makes a similar step," said President Mahmoud Ahmadinejad in an interview with a German newspaper. "We hope that we will make progress in Moscow."

On Friday, Saeed Jalili, the Iranian negotiator said: "We expect that Iran´s right to nuclear technologies, including uranium enrichment, will be recognised and respected."

Western officials say that a successful meeting would see a serious response from Iran to the offer on the table. But this opening proposal is significantly more far-reaching than it might appear.

Iran has a much bigger stockpile of uranium enriched to the lower 3.5 per cent purity needed for nuclear power stations. Ostensibly, the opening proposal does not apply to this material. In practise, however, these reserves are now being used for further processing to the 20 per cent level, supposedly to fuel a civilian research reactor in Tehran.

Taking this step also brings Iran much closer to producing uranium at the 90 per cent purity needed for nuclear weapons. "Iran´s entire uranium enrichment programme is now being devoted to producing 20 per cent enriched uranium," said Olli Heinonen, a former deputy head of the International Atomic Energy Agency.

If Iran accepted the proposal on the table, it would effectively be agreeing to freeze the main effort of its nuclear programme. Far from starting with small steps, the current negotiations are demanding a very significant move from Tehran at the very outset. (© Copyright of Telegraph Media Group Limited 2012. 06/18/12)