By Gabriel Gatehouse
BBC News, Baghdad
Saleh al-Mutlaq is now running on a secularist platform
Preparations for the Iraqi parliamentary elections have been thrown into chaos by a row over whether or not to uphold a ban on hundreds of candidates, because of alleged links to Saddam Hussein's outlawed Baath Party.
The start date for campaigning has been postponed and the Iraqi parliament will hold an emergency session on Sunday to debate the issue.
The dispute reflects both the sectarian fault-lines within Iraq and geopolitical tensions between Washington and Tehran.
Amid the multitude of different Arab parties and coalitions competing for seats in this election, it is possible to discern two more or less distinct political directions.
One draws its support broadly from Iraq's majority Shia population and is to a greater or lesser extent sympathetic to the government in Tehran.
The other relies largely on Sunni Arabs and secularists whose policies range from Iraqi and pan-Arab nationalism to open nostalgia for the relative stability of the Saddam-era.
The roughly 500 politicians at the centre of this row include both Shia and Sunnis.
But the Commission which has drawn up the list is headed by a Shia with close ties to Iran.
US withdrawal impact
Ali al-Lami was briefly arrested - and later released - by the US military in the summer of 2008 on suspicion of masterminding an attack on their forces, with Iranian support.
The US wants all combat troops out by September 2010
Mr al-Lami is himself standing in the election. The most prominent name on the list of banned candidates is a Sunni.
Saleh al-Mutlaq is a former Baath party member, now running on a secularist ticket with the former Iraqi Prime Minister Ayad Allawi.
Critics say that the exclusions are nothing more than a crude attempt to boost the electoral prospects of Shiite candidates, including the Prime Minister, Nouri al-Maliki.
On the other side of the argument are those who believe passionately that a continued process of de-Baathification is essential for Iraq to complete the transition from dictatorship to democracy.
But this row is about more than just the past. US officials have made it clear they are uneasy about the exclusions, partly because they fear for the credibility of the election among Sunni voters.
The White House is now focused on its timetable for withdrawal: all US combat troops are due to be pulled out by this September in preparation for a full military departure by the end of 2011.
What impact will that have on American influence in Iraq? The answer depends on what kind of government the people elect in March.
Iraq has become a key battleground for geopolitical power between the United States and Iran.
Each side wants the new administration to be sympathetic to its aims. But the continuing tensions that exist between Tehran and Washington may make those aims mutually exclusive.