Iran crisis: Can conflict be averted?
The long-running crisis between Iran and the West appears to be deepening by the day.
A whole series of events - preparations for stepped-up US and Western sanctions against Tehran, Iran's warning to a US aircraft carrier to stay out of the Gulf, the sentencing to death for alleged spying of an American with dual Iranian-US nationality, and the killing of yet another Iranian scientist, which Iran sees as part of a continuing foreign campaign to sabotage its nuclear programme - all add to the sense of drama and a belief that in some way this crisis is coming to a head.
Iran's announcement this week that it has begun uranium enrichment work at the Fordo facility near Qom confirms the fact that the Tehran government, for all the sanctions and the tough talk, is determined to press ahead with its nuclear programme - the very heart of the disagreement between Iran and the West.
Discussion of potential military action has swung from the likelihood of Israeli or US air strikes against Iran's nuclear infrastructure to the possibility of a serious maritime clash in the Gulf should Iran seek to close the Strait of Hormuz with the Americans seeking to reassert the right of free passage.
The story of Iran's turbulent relationship with the West is best described by the complicated intersection of two timelines - the imposition of ever tougher economic sanctions on the one hand and Iran's progress in its nuclear research effort on the other.
Crisis points generally loom when new sanctions are being considered and the current case is no exception.
Paul Pillar, a veteran US intelligence expert now at Georgetown University, provides a different analogy.
He likens tensions between Iran and the US to "a spiral in which each new incident feeds animosity which in turn encourages still more unfriendly actions from the other side".
"It is a classic case of hostility begetting more hostility in return," he says.
The US is working up a new round of restrictions on Iran's central bank and the European Union is moving towards strict curbs on Iranian oil imports.
Washington is also trying to expand their impact by persuading Iran's key customers in the Far East to scale back their involvement with Tehran.
China may be unwilling to play ball but Japan and the South Koreans may be more amenable to US persuasion.
With every sign that the Iranian economy is beginning to feel the pain from sanctions, it is little wonder that things are getting tense.
Iran's threat regarding the closure of the Strait of Hormuz is a clear attempt to warn the West that the imposition of reinforced sanctions may have an effect on Western economies, too.
In other words that Iran can apply "sanctions" of its own.
Paul Pillar says that under present circumstances there seems little possibility of a true turning point in this crisis.
"Iran clearly is feeling pain from the sanctions but this is not a turning point as long as Iran is not given any room in which to turn," he says.
"Diplomatic avenues for exploring ways in which a peaceful Iranian nuclear programme could continue under adequate safeguards remain largely unexplored.
"Iranian leaders probably believe the true objective of the West and especially the United States is regime change, not an agreement," Paul Pillar says. "The West has given the Iranians little reason to think otherwise."
Of course there is a third timeline operating at the moment that is having an influence on events and that is the US presidential cycle.
The race for the Republican nomination is well under way and the extent to which Iran has figured in the would-be candidates' pronouncements is remarkable.
"The US presidential election campaign is a significant factor in contributing to the current tensions with Iran," argues Mr Pillar.
"With little other basis for criticising President Barack Obama's foreign policy successes (including completing the withdrawal from Iraq and eliminating Osama Bin Laden), all of the Republican candidates - except for Ron Paul - are trying to outdo each other in sounding bellicose about Iran.
"Tehran will interpret this rhetoric as another indication that the United States is implacably hostile and the opportunity for agreements is minimal."
This is all rather perplexing since this current crisis comes on President Obama's watch and is a direct result of the tougher round of sanctions he now proposes.
The vague ideas of an opening to Tehran which characterised some of the president's earliest pronouncements are long-forgotten.
The Obama administration has also not been slow to warn Iran that the US Navy would act to keep open the Strait of Hormuz.
In that sense Mr Obama is closer to the brink of conflict with Iran than any other recent administration.
Hostilities may be avoided for now, but for many US experts and political pundits alike there seems to be a growing sense of pessimism - a belief that the US and Iran will come to blows at some point.
And that is a very dangerous situation to be in since expectations can have an important bearing on how events unfold.CLICKABLE
Massoud Ali Mohammadi
A physics professor at Tehran University. Died 12 January 2010 outside his home when a motorcycle rigged with explosives detonated next to his car.
A member of nuclear engineering faculty at Shahid Beheshti University. He was killed in Tehran 29 November 2011 when a bomb was attached to his car by a motorcyclist.
Fereydoon Abbasi Davani
The future head of the Atomic Energy Organisation of Iran. He was injured 29 November 2011 when a motorcyclist attached an explosive device to the side of his car.
Mostafa Ahmadi Roshan
A professor at the Technical University of Tehran and senior supervisor at the Natanz uranium enrichment facility. He died 11 January 2012 after a bomb was placed on his car by a motorcyclist.