How quickly could Iran prepare a nuclear bomb?

Estimates on when Iran may be able to perfect uranium enrichment and produce enough fissile material for its first nuclear weapons -- if indeed this is the goal of current Iranian efforts -- range from 24 months to as long as eight years. Yet the most credible estimates suggest this process may take at least three to five years.

Although there is uncertainty over the number of active centrifuges spinning away in Iran, the country's engineers are undoubtedly making slow progress towards mastering the enrichment of uranium.

Despite the regime's grandiose claims of technical breakthroughs, Iran's nuclear programme is unlikely to have made a quantum leap over the past year:

• President Mahmoud Ahmadi-Nejad claimed two weeks ago that Iran has 3,000 active centrifuges to enrich uranium and is pressing ahead with its programme.
• This is at odds with the conclusion of the IAEA quarterly report, which showed the programme flagging and some distance from the 3,000 mark, which would constitute 'industrial scale' enrichment.

Iran is pumping uranium gas into these units. Uranium gas, spun in linked centrifuges, can result in either low-enriched fuel suitable to generate power, or the weapons-grade material that forms the fissile core of nuclear warheads.

But centrifuges need to work continuously for several months to enrich uranium efficiently. It is unclear how long the existent centrifuges will be able to operate, as up to 50% of units previously installed had failed within the first three weeks.

Tehran claims it has enriched small amounts of material to 4.8% U-235, which is good for use as fuel in a nuclear power reactor. If it pushes ahead unchallenged, it will be able to perfect the ability to enrich uranium via centrifuges, even to the very high levels needed to produce a nuclear device. If Tehran can overcome the remaining technical hurdles to centrifuge production and operation the country could join the nuclear club before the beginning of the next decade -- although most credible analysts, including the US intelligence community, suspect that the process may require more time.