Talk to almost anybody in Washington about foreign policy these days and you are likely to hear that Iran is the number one "international problem" for the United States. Pundits and politicians are unanimous that dealing with the Islamic Republic will be one of the key issues of the presidential election campaign.

The question is: what to do about Iran?

It is clear that the leadership in Tehran, boosted by last week's parliamentary elections, is in no mood to offer concessions.

The choice facing policymakers is between standing up to the Islamic Republic, even if that would mean military conflict, and acknowledging its right to pursue whatever policies it desires even if that meant threatening the vital interests of the Western democracies and their regional allies.

To avoid that choice, Senator Barack Obama, the front-runner as the Democrat Party's presidential nominee, has announced that, if elected, he would invite the Islamic Republic's President Mahmoud Ahmadinejad for "unconditional talks."

This means that Obama would reverse the Bush administration's policy on Iran and ignore three unanimously approved United Nations Security Council resolutions that call on the Islamic Republic to suspend uranium enrichment as a precondition for talks.

However, Obama is no longer alone in his call for "unconditional talks" with Ahmadinejad.

Last week, Henry Kissinger, a foreign policy advisor to Senator John McCain, the Republicans' presumptive nominee for president, also called for unconditional talks with Tehran.

A few days after Kissinger's change of position, it was announced that Admiral William J Fallon, Commander of the US forces in the Middle East, had resigned because he disagreed with the administration's policy of keeping the military option open against the Islamic Republic.

Fallon is reported to have opposed plans for intercepting Iranian ships suspected of carrying dual-use products. Instead, the admiral urged his political bosses to think of talking to Tehran.

Then it was the turn of Dennis Ross, a former US peace-broker in the Middle East, to call for unconditional talks with Tehran.

Ross proposed that the talks be coupled with increased sanctions against Tehran with the help of the European Union, Russia and China. To achieve that, he proposed concession to Russia including scrapping US plans to install anti-missile units in Poland and the Czech Republic. (EU and China would also receive unspecified concessions from the US in exchange for harsher sanctions on Iran.)

All this talk of talking to Tehran may well sound eminently reasonable.

However, even if we ignore Ross's weird suggestion to make Tehran angrier by imposing harsher sanctions while inviting it to negotiate a deal, the "talk to Iran" idea is problematic for other reasons.

The first problem is to decide what the talks are going to be about.

The Islamic Republic has never said it was not prepared to talk.

It has been engaged in a dialogue with the EU since 1980 and maintains a cordial conversation with many other countries, among them Russia and China. It has also held secret talks with the US, in 1979, 1985-86, and, more recently, 1999-2000, in addition to public sessions over Afghanistan and Iraq in 2002 and 20007.

The only thing that the Islamic Republic is not prepared to talk about is stopping its uranium enrichment programme as demanded by the Security Council.

To avoid that hurdle some advocates of the "talk to Iran" policy suggest that the uranium enrichment issue not be mentioned. Instead, as Kissinger has put it, the US and its allies should ask Iran to scrap the military aspect of its nuclear programme, thus permanently abandon its right to develop atomic weapons.

The problem is that the Islamic Republic has never admitted it had a programme to build the bomb.

What Kissinger demands is that the Tehran leaders first admit that they ad been lying all the time and had had plans to build the bomb but are now prepared not to do so.

Can Kissinger seriously expect the Iranian "Supreme Guide" Ali Khamenehi to make such an admission?

Even if Tehran leaders were prepared to admit they had been lying, and that they would scrap a programme that they had claimed did not exist, they might still find it hard to offer the undertaking that Kissinger and others demand.

Why should Iran become the only country in the world to abandon the right to develop nuclear weapons?

After all, it is not illegal to acquire the technology to make nuclear weapons or even to manufacture and deploy them.

Some countries, such as Argentina, Brazil, South Africa, the Ukraine, Kazakhstan and most recently Libya, have voluntarily abandoned that right and scrapped their military nuclear programmes. Nevertheless, even they have not foresworn their right forever and could decide to revive their nuclear programmes any time they wished.

In other words, the "talk to Iran" chorus suggests that Tehran be asked to do something that no self-respecting government would contemplate.

The method that the "talk to Iran" chorus suggests could have disastrous results for all concerned.

It could persuade Tehran that it had already won and that it could ignore the three Security Council resolutions without risk. After all, unconditional talks means that the major powers have dropped their demand that Iran suspend uranium enrichment before engaging it in substantial negotiations about future relations.

Also, Tehran may offer concessions on a range of issues, for example sacrificing Hezballah and Hamas and even Syria, in exchange for a tacit acceptance of its nuclear ambitions by the US and its allies. That would put the Western negotiators in a quandary: granting Tehran a big and irreversible prize in exchange for smaller and reversible concessions. Tehran could activate or de-activate its Syrian, Hezbollah and Hamas pawns any time it wished as it has done with Muqtada al-Sadr in Iraq. However, once Tehran has the bomb no one would be able to put the genie back into the bottle.

The only way the Islamic Republic might abandon its nuclear ambitions is under duress when it realises that the cost of making a bomb, if that is indeed the aim, is much too high in terms of economic suffering, diplomatic isolation and/or military defeat.

Seen from Tehran, the idea of "unconditional talks" looks like a form of surrender by Western powers.

It could strengthen the most radical elements within the regime who could then dismiss their critics as cowards or traitors.

There is another, perhaps more important problem, with the "unconditional talk" policy. It could be tried only once.

If it fails to persuade Tehran to offer the only concession that matters, that is to say stop making raw material for a bomb, the only choice left for the US and its allies would be surrender or the use of force.

In one of those ironies of history, advocates of "unconditional talks" with Tehran may make war more not less likely.