Vote USA 2008 issues: Iran

Although Iraq is the biggest foreign policy issue in the election, Iran is running a close second.

Many US voters are concerned about Iran's nuclear ambitions, and in particular about its uranium enrichment programme, which it concealed for many years.

A US intelligence assessment published in December 2007 concluded that Iran had halted a nuclear weapons programme in 2003, but President Bush has stressed that Iran is "still dangerous".

Like Democrats, Republicans talk about the need for diplomacy with Iran - but are much keener to stress their willingness to use military force Q&A: Iran nuclear row America's Israeli option on Iran

The US also accuses Iran of arming Shia militias in Iraq, and destabilising peace in the Middle East by backing militant groups such as Hamas and Hezbollah.

When a resolution was passed by Congress classifying a section of Iran's Revolutionary Guard as a "terrorist organisation", some commentators suggested that this would give the White House the legal authority it needed to mount an attack on Iran - an idea that appears to have been actively promoted by some members of the administration.

There were signs that the US and Iran might be opening the door to diplomacy when, in July, a senior US official for the first time attended international talks with Iran over its nuclear programme.

But Iran's continued defiance of successive Security Council ultimatums to freeze uranium enrichment has led to new UN, EU and US sanctions.

Democratic presidential candidate Barack Obama has stressed the need for diplomacy, and a co-ordinated international effort to impose tougher economic sanctions if necessary.

He has pledged to "meet directly with Iranian leaders" without preconditions, saying he would "engage in a level of aggressive personal diplomacy".

He has not taken the military option off the table, however.

'Military posture'

Republican presidential candidate John McCain has accused Mr Obama of displaying "inexperience and reckless judgement" in his readiness to talk to Mr Ahmadinejad.

Mr McCain has talked about the need for international diplomacy on Iran, but has stressed his willingness to use military force.

He has said the US should "bolster its regional military posture" to make clear to Iran that the US will act to protect its forces in Iraq and to deter Iranian involvement there.

In response, Mr Obama has suggested Mr McCain wants to continue the Bush administration's "failed policy" of talking tough on Iran, but being ignored by its leaders.

Mr McCain sparked criticism last year after a town hall meeting in South Carolina at which he sang the Beach Boys' song "Barbara-Ann", jokingly changing the words to "Bomb Bomb Bomb Bomb Bomb Iran".