'EU big-3's nuke deal with Iran falling apart'

But nearly nine months on, diplomats are cannily admitting their bid to strip Iran's ruling clerics of gaining A-bomb potential is falling apart. And perhaps more alarmingly, there does not appear to be a great deal that they can do about it.

The problem, say diplomats who were close to hammering out the "Tehran declaration", lies not so much with Iran's recent backing away from certain technical aspects of it, but with its firm rejection of the accord's more ambitious premise.

"We wanted the same kind of agreement with Iran as what we had with Libya. Iran had an opportunity to abandon its more sensitive nuclear work, and in return win greater trade and better relations with the West," recalled the senior diplomat.

This was an effort to get around the inherent weakness of the nuclear Non-Proliferation Treaty (NPT) -- a text of good intention in so far as member states are allowed to master the entire nuclear fuel cycle for peaceful purposes as long as they commit themselves not to take the relatively easy next step to military usage.

"Iran is a special case. There was a pattern of years of deception, so we needed to go beyond the NPT," explained another EU diplomat working on the nuclear dossier.

"We wanted Iran to give up the nuclear fuel work in exchange for guaranteed supplies of fuel from overseas, as well as improved trade and diplomatic relations."

But for Iran's 25-year-old Islamic regime, it was an existential leap too far.