By Frances Harrison
BBC News, Tehran
What will alarm Tehran about the latest details of US military planning for a strike on Iran is the fact that there are now two possible triggers for an attack.
One is, as expected, the nuclear programme. But the new one is any major attack on US forces in Iraq that could be traced back to Iran.
Iraninan technician at the Isfahan Uranium Conversion Facilities
With the head of the UN nuclear watchdog Mr ElBaradei saying it could take Iran another six to 12 months to get 3,000 centrifuges running, and four to six years to be able to produce a bomb if it wanted one, there is still time for negotiations on the nuclear front.
But it is tensions over Iraq that have escalated sharply in recent weeks with the US arresting Iranians they say are members of the elite Qods Brigade of the Revolutionary Guards.
There is also a feeling among many analysts that the US has started building a case for war against Iran over its alleged interference in Iraq.
For many in Iran it seems unfair that the full blame for the violence in Iraq is suddenly being put on them and not on Sunni Arab countries that also back groups inside Iraq.
They argue that the disintegration of Iraq is not in Iran's interests and they would like a stable neighbour with a predominately Shia government in power.
The US making public their targets for a possible military strike on Iran is likely to be seen in Tehran as part of ongoing Western pressure.
In public, Iranian officials always brush off such news as psychological warfare by the US.
The timing - just before the 21 February deadline set by the UN for Iran to halt its nuclear programme - is also likely to be seen as a threat intended to persuade Iran to back down.
Iran's Natanz uranium enrichment plant
In the Iranian establishment it appears there are deep differences of opinion about how grave the situation is.
Many reformists and moderates are very worried America is preparing for war, but hardliners like President Ahmedinejad seem to dismiss the risk believing their own propaganda that Iran is too powerful a nation to be attacked by the West.
Some take a middle position - arguing that the talk of war is a bluff - a means to pressure Iran. But they concede there is a possibility of an accidental war if Iranian Revolutionary Guards, for example, retaliated against US forces in Iraq.
They compare the situation to the kidnapping of two Israeli soldiers last summer by Hezbollah in Lebanon which triggered the war there.
The argument is that if America provoked Iran enough by arresting key military figures inside Iraq then their colleagues might be tempted to take revenge and perhaps kidnap US soldiers which would provide an excuse for air strikes on Iran.
Among the Iranian people there is not much awareness of the drum beats of war. The local media is heavily controlled and censored and many Iranians do not speak a foreign language to allow them to access the international press.
Independent websites in Persian have been filtered by the government, including the BBC's own Persian language site, in what some here believe is a deliberate attempt by the government to keep its own people in the dark.
Unsubstantiated rumours circulate about when an attack might come but everyone goes about their lives as normal.
There is no sense that people are preparing for difficult times ahead - but there is uncertainty and confusion about the future.