The Big Question: Is Iran developing a nuclear bomb, and if so, should it be stopped?

What's changed since the election of President Ahmadinejad?

A lot - his election brought about an instant deterioration in the diplomatic atmosphere. Following his victory last June, the Iranians adopted a much more defiant tone with the three European powers - Britain, France and Germany - that had been leading negotiations in the hope of persuading Iran to curb its nuclear programme in return for economic incentives. His inflammatory statements about Israel and the Holocaust shocked world leaders and fuelled concern about the possible consequences of such a regime possessing a nuclear weapon.

Why are there suspicions that Iran is building a bomb?

In part, because of the deficit of trust caused by Iran's concealment of key elements of its nuclear programme from UN weapons inspectors for 18 years. But the main suspicions stem from Iran's refusal to answer technical questions from the International Atomic Energy Agency in order to provide the reassurance that the Iranian programme has remained within legal limits. Iran's reluctance to provide full documentation and answers led the IAEA chief, Mohamed ElBaradei, to conclude that he cannot guarantee that Iran's nuclear programme is solely for nuclear energy. There is also concern over Iran's missile development. Iran announced last month it had test-fired its Shahab-3 missile, capable of striking Israel. So countries like the US, Britain and Israel - which already have nuclear weapons of their own - want to ensure the suspension of uranium enrichment by Iran as a guarantee against the Iranians developing a nuclear warhead. They say that they are not opposed to Iran having a nuclear fuel cycle, but that any uranium enrichment must take place outside Iranian territory to prevent any diversion towards military activities.

What is Iran's position?

Iran wants to pursue its uranium enrichment programme which is its right under the nuclear non-proliferation treaty - as long as the goal is nuclear energy. The Iranian leadership says its intentions are purely peaceful, and that the oil-rich nation needs to diversify into nuclear energy due to demographic pressure. Iran's only working nuclear reactor was built by the Americans in the time of the Shah, when the US had no problem with the idea of Iran producing 23,000 megawatts from nuclear power. So Iran says this proves the limits which are now being set on its uranium enrichment are politically motivated. There is some uncertainty about how representative Mr Ahmadinejad's hardline views are within the Iranian leadership, as prominent Iranians such as his opponent in the presidential election, Ali Akbar Hashemi Rafsanjani, have expressed public reservations. But for now, the country's supreme leader, Ayatollah Ali Khamenei, has not seen fit to distance himself from the president.

What do the experts think?

Western think- tanks, and former UN inspectors, suspect that Iran wants to keep its options open, by proceeding with nuclear research to a point that would allow it to break out and build a bomb as an insurance policy against attack. Iran could have the capability of building a weapon - if it breaks out of UN controls - within five years.

Why is everyone so emotional?

Because of decades of mistrust. Iran has serious reasons to suspect that Britain and the US may be more interested in regime change than in a negotiated solution of the nuclear stand-off. The two countries engineered the 1953 coup that overthrew the elected prime minister, Mohammad Mossadegh. Iran's relations with America were abruptly ended by the 1979 hostage-taking at the US embassy in Tehran. That is why the US has continued to reject any suggestion of direct talks with Iran, which is seeking security guarantees as part of a bargain under which it would curb its nuclear programme. But emotions are also running high between Britain and America on the one hand, and Russia and China on the other because of the Iraq precedent. All four countries serve on the IAEA board and are veto-holding powers on the UN Security Council. Memories are still fresh of how Britain and America went to war on Iraq, accusing Saddam Hussein of defying the international community over its weapons programme, after bypassing the Security Council.

Why has the UN Security Council got involved now?

The European powers and the US led the drive to refer Iran to the Security Council after the board of governors of the IAEA - the UN nuclear watchdog - found Iran in non-compliance of the Non-Proliferation Treaty last September. Russia and China, which are arguing for a diplomatic solution to the impasse, would prefer the dispute to remain with the IAEA, ie at a technical level. But they did not block the referral to the UN, when the IAEA governors decided that additional political pressure was required.

What are the options now?

The Bush administration says it wants a diplomatic solution, which is why the issue is now before the UN, although the military option remains on the table. But the US, and EU, are already considering possible sanctions which could be taken by individual countries if the UN route fails. Iran could strike back by using its oil card, although Iranians would suffer because the country needs to import refined oil products. If Israel, or the US, decide to stage unilateral strikes on Iran, the Iranians could hurt both countries' vital interests thanks to their influence in Iraq, and on militant Islamic groups throughout the Middle East. Of course, Iran could always back down and agree to suspend uranium enrichment in order to avert international isolation. But that seems unlikely at this stage.

Should we be concerned that Iran may be developing nuclear weapons?

Yes...

* It is feared that President Ahmadinejad might decide to carry out his ambition to "wipe Israel off the map"

* Iran's spiritual leader has already offered to share nuclear skills with Sudan, a regime few would like to see with that knowledge

* Other states in the region could be encrouaged to go nuclear

No...

* Brazil just opened a uranium enrichment facility for nuclear power so why shouldn't Iran be allowed to do so as well?

* Even if Iran did build a bomb by breaking out of the non-proliferation treaty, its only rational use would be as a deterrent.

* Iran could be a counter-balance to nuclear-armed Israel