The urgent discussions about bombing nuclear facilities in Iran return us to the armed attack that was launched on Iraq under US and UK leadership in March 2003 to eradicate weapons of mass destruction – weapons that did not exist. That intervention was criticised severely and, I think, rightly as a violation of the UN Charter: it could not be justified as an act of self-defence and, despite some efforts by the UK, it had not been given any authorisation by the UN Security Council.

The only positive result was the toppling of a brutal tyrant. If Iran were to be bombed, it would be another action in disregard of the UN Charter. There would be no authorisation by the Security Council. Iran has not attacked anybody and despite Mahmoud Ahmadinejad's wild, populist declarations that Israel should be wiped off the map there is no imminent Iranian threat that could be invoked to justify pre-emptive action. It would be a war aiming chiefly to prevent Iran from enriching uranium – a preventive war.

While the Iran impasse today has some important similarities with the Iraq issue, the situations also differ in several respects. Iraq in 2003 was exhausted and a military threat to nobody. Iran today may be weakened economically, torn by internal strife and somewhat hurt by sanctions, but it retains a good deal of military power and is seen as a threat by many countries in the region. Iran has slowly developed a capacity to enrich uranium. As the programme cannot be economic, many suspect that the main and ultimate intention is to produce weapons-grade nuclear material.

During the Iraq-Iran war in the 1980s such an intention would have been natural. In 1981 Israel destroyed the Osirak nuclear reactor and Saddam Hussein was, indeed, aiming for a nuclear weapon. At the present time Iran can hardly worry about a nuclear Iraq, but it may have a wish to assert itself and defy the states that ostracise it and seek its isolation. It is possible – but is denied by Iran and not evident to me – that there is a determination to make a nuclear weapon. Whether this is so or Iran only seeks to get close to the option, Israel and other states as well are concerned about the threat and the risk of nuclear proliferation that would be posed by a nuclear-armed Iran.

For a number of years, the UK, France and Germany – the E3 – later joined by the US, Russia and China to form the P5+1 (the permanent five on the Security Council plus Germany), have sought to persuade Iran to suspend the enrichment programme. Assuming that Iran would calculate the cost-benefits of the scheme, they have made a number of positive offers in return for its suspension: assurance of external supplies of uranium fuel, assistance in building more nuclear power plants in Iran, facilitation of investments and support for Iranian membership of the World Trade Organisation, and a confirmation to Iran of their respect for the UN Charter's provisions that ban the threat or use of force.

While the approach has been far from a diktat, the manner of presentation has sometimes been condescending: for a time, suspension was made a precondition for sitting down to talk. Iran was sometimes told to better its behaviour – as if the country were an unruly minor. Whatever might have been the impact of such tones, Iran steadfastly rejected all demands to suspend the enrichment programme, which led the Security Council to work the cost side and impose sanctions.

As these sanctions have not had any effect – and as Russia and China, and probably other states on the Security Council, would be opposed to stiffer measures – Israel has resorted increasingly to covert action in Iran and so has the US. For instance, Iranian enrichment activities were delayed by an action, believed to have been undertaken by Israeli and US units, to implant a computer virus (Stuxnet) in Iranian centrifuges. Iranian nuclear experts have been assassinated. Last month, the US secretary of state, Hillary Clinton, condemned a recent case of this outrageous, gangster-style war.

Prelude to a showdown

As the benefits offered and costs imposed under Security Council-mandated sanctions and covert actions have led Iran not to waver from pursuing its enrichment programme but rather to expand it, nervousness has increased. Some have asserted that the talks and Security Council sanctions have led nowhere and that only rigid financial sanctions, an embargo on Iranian oil and the threat of armed action could prompt Tehran to abandon the path to the nuclear bomb.

These attitudes received a boost through a report presented by the International Atomic Energy Agency late last year. Basing its findings not only on observations from a vast number of inspections of its own but also on intelligence material supplied to it by IAEA member states (much of it publicly known earlier), the agency concluded that efforts to develop nuclear weapons could explain some activities in Iran, while other activities could hardly be explained in any other way. The IAEA did not, however, conclude that Iran was making a weapon or had taken a decision to make one.

The agency's conclusions were contested by Iran and the reliance on national intelligence was questioned by some. The experience of the IAEA in 2002 and 2003, and of the UN Iraq inspections that I led, certainly suggest prudent use of national intelligence. The infamous alleged contract between Iraq and Niger for the import of uranium oxide had been cited by George Bush in his State of the Union address, but the agency discovered that it was a forgery. In the UN inspections, national intelligence supplementing our own data once very nearly led me to assert that Iraq still had a substantial quantity of anthrax. However, I stopped short of an assertion because, in my view, the intelligence was not adequately backed by evidence. After the war it emerged that the anthrax had been destroyed and buried close to Saddam's residences, a fact that our counterparts presumably did not want to make known.

Noting these cases from 2002 and 2003 is not to criticise the provision or receipt of in­telligence. Such information may offer a very useful basis for questions by the IAEA to a state that it is inspecting. It may lead it to request inspections at specific sites or of specific activities. In my view, the agency should not, however, draw conclusions from information where the supplier is not ready also to show evidence. Both Mohamed ElBaradei and I were careful on this point and I hope the present director general of the IAEA, Yukiya Amano, follows that line. The agency should not risk its own credibility by relying on data that it cannot verify fully.

While the recent IAEA report on Iran and its use of national intelligence caused an international stir, neither its contents nor the country's obstruction of inspections of declared nuclear sites or material seem to be behind the recent sharp increase in tensions and fear of Israeli military action. It appears to be due rather to the information from agency inspection reports that the Fordow Fuel Enrichment Plant (near the city of Qom) may be close to beginning operation. While the country's largest underground installations for enrichment at Natanz, in central Isfahan Province, might be successfully stopped by bombing, this might not be possible at Fordow. Hence some, notably in Israel, take the view that a showdown with Iran would be desirable before Iran acquires an enrichment capability that might be immune to effective attack from the outside.

Others – and I am among them – believe that bombing Iranian nuclear installations may be a path to disaster rather than to a solution. Iranian leaders are not going to sit quietly and twiddle their thumbs. The Middle East is packed with missiles and full of oil, gas, pipelines and tankers that can burn.

A war in the Gulf and skyrocketing of oil and gas prices is not exactly what a financially troubled world needs right now. Furthermore, not all relevant installations in Iran would be destroyed. Some may not be known. The capacity and know-how to produce more centrifuges will survive and after armed attacks the Iranian government, which many now hate, may get broad support in a nation feeling humiliated by the attack. If there was not already a decision to go for a nuclear weapon it would then be taken. An Iranian postwar return to enrichment would also likely lead other countries in the Middle East to go the same way, making the area even more volatile.

Red lines

So, what can be done and what will happen? I am convinced that while the Bush administration itched for the war in Iraq, the Obama administration seeks to avoid being drawn into armed action in Iran. Israeli leaders keep the idea in the headlines, but the US appears to try to discourage them. The chairman of the US Joint Chiefs of Staff, General Martin E Dempsey, is even reported to have told Israeli leaders that the US would not take part in a war with Iran begun by Israel without prior agreement with Washington.

Naturally, a democratic US administration cannot allow itself to look soft on a matter touching the security of Israel. President Obama evidently feels obliged to repeat that "all options are on the table", a mantra that is perhaps less likely to scare Iran into concessions and submission than to suggest to it to arm itself as fast as possible. Nevertheless, he has moved a war-fatigued US out of Iraq and wisely wants out of Afghanistan. The administration does not want to be drawn into a third costly war in the Middle East, and it has taken some steps in the past few weeks to lower the temperature. It has agreed with Israel to put off a joint military manoeuvre and the US secretary of defence, Leon Panetta, has said that Washington draws the red line at an Iran producing a nuclear bomb – rather than achieving a capacity to produce the weapon. In Congress, US intelligence leaders have said that although they see the Iranians moving ever closer to the ability to weaponise, they do not believe that there has been a decision to go ahead with a nuclear bomb.

There are ominous signs: US aircraft carriers and UK and French naval units in the Persian Gulf, Israeli military manoeuvres in the eastern Mediterranean and Iranian talk about closing the Strait of Hormuz. A meeting is expected soon between Iran and the P5+1 – perhaps in Istanbul. The European Union's high representative for foreign affairs, Catherine Ashton, has said that the EU decision to start an oil embargo from the end of June is designed to bring the Iranians to the table. One would hope it is not only to ask them to kneel.

Cost against benefit

The ambition for the coming meeting should be to lower the temperature, to reduce the risk of a resort to armed force and to set the stage for further talks. Rather than rubbing in the cost to Iran of a continued impasse, the P5+1 could confirm that their previous offer of benefits remains on the table and that they are open to discuss further items of mutual interest.

For its part, Iran could simply confirm that it will remain a party to the Non-Proliferation Treaty, recognises and abides by its obligation not to make a nuclear weapon, will continue to enrich as before (that is, to a level not higher than 20 per cent) and will accept IAEA inspections as before, in both Natanz and Fordow.

Under a slightly more ambitious approach, the meeting could discuss the revival of an idea of enabling Iran to obtain the 20 per cent enriched fuel needed for a research reactor that produces medical radioisotopes – and in return export the country's stock of indigenously produced 20 per cent fuel.

Further meetings could be scheduled with a scope that would permit the negotiating sides to bring in a greater variety of mutual interests – for instance, regarding Afghanistan or the suppression of terrorism, whether promoted by Iran or promoted by others in Iran.

One more meeting is already scheduled. At the review of the Non-Proliferation Treaty in New York in 2010, it was decided that a conference on a Middle East free of weapons of mass destruction should be convened before the end of 2012. It is scheduled to take place in Helsinki. The idea of a nuclear-weapon-free zone was originally advanced in 1974 in a UN General Assembly resolution sponsored by Egypt and Iran. The focus at that time was obviously on Israel's nuclear weapons. Today, Iran's programme of enrichment is just as much the concern. There is a risk not only of a further spread of weapons in the Middle East but also of a spread of enrichment plants and installations producing plutonium, creating near-nuclear-weapon states.

To many, the idea of an agreement between the parties in the Middle East – including Israel and Iran – to renounce not only the possession, acquisition or development of weapons of mass destruction, but also the means of their production, might seem very remote. It does not seem far-fetched to me.

It would, to be sure, call for many difficult arrangements, including verification going beyond IAEA safeguards, as well as outside security guarantees and assurances of supply of nuclear fuel for civilian reactors. It would require that Israel give up its nuclear weapons, stocks of fissile material and capability to produce enriched uranium or plutonium. It would require Iran to do away with its enrichment plants and a number of other installations. All states in the zone would agree between themselves not to acquire or develop capabilities for the enrichment of uranium or production of plutonium. Iran would lose investments made in some nuclear installations, but it would continue to build electricity-generating nuclear power reactors and be credited with having helped to eliminate the Israeli nuclear weapons and achieve important disarmament in a dangerous corner of the world. Israel would lose its nuclear weapons, but it would also be freed from concern about the nature of future nuclear programmes in the region – whether in Saudi Arabia, in Egypt or in Turkey.

I am not surprised that a recent poll reported that a majority of Israeli Jews say they think it would be better that no state in the Middle East should have nuclear weapons than that two states should have them. Presumably, this majority is of the view that the Israeli nuclear weapons are not a very useful part of the defence of the country or, at any rate, that the benefit of doing away with them is greater than whatever it would cost.

I suspect that, similarly, a majority of Iranians would think the enrichment part of Iran's nuclear programme is not essential or, at any rate, that the benefit of nuclear disarmament in the Middle East would be greater for Iran and for the world than the cost to Iran of abandoning uranium enrichment.

Hans Blix is a former director general of the International Atomic Energy Agency. He led the search for "weapons of mass destruction" in Iraq