BBC News Online's Tarik Kafala

Saddam Hussein has governed Iraq with an iron grip since 1979.

It is a commonly-held belief about the country that his often brutal rule has been the glue holding its fractured communities together.

I believe one must plan not just for the disappearance of the regime but for what takes its place... It is not clear to me that this has been thought about by the administration Richard Murphy, Former US Assistant Secretary of State

His family's control has been so dictatorial that there are no real political institutions that might take over the running of the state if he were deposed. What could follow is a chaotic power vacuum.

Iraq has no serious internal opposition, and there are doubts about the various organisations that have set themselves as opposition groups in exile - some are badly run and disunited, others have no popular support in Iraq at all.

The army, widely seen as the institution to keeping control of the country, may be the key to deposing Iraq's ruler and keeping the country in one piece.

Reports in the US press have said that the US administration is considering a plan to occupy Iraq and install a US-led military government as a way of avoiding the country's chaotic disintegration.

Three-way split?

Officially, Middle Eastern governments would rather see Saddam Hussein stay in power than face the prospect of civil war and the break-up of the country.

If Saddam Hussein lost power it is possible that Iraq would fragment into three entities controlled by the Kurds in the north, the Shia Muslims in the south and Sunni Muslims in the centre.

To many, the creation of a southern Iraqi state run by Iraq's majority Shia community would represent a victory for the influence of radical Iran.

I don't think that Washington is very much concerned with what might happen after Saddam is toppled, I think they believe that the event will produce a pro-American regime, and that there is no real possibility of a anti-American one Mustapha Alani, Royal United Services Institute

Turkey, Iran and Syria also fear the rise of Kurdish nationalist and separatist movements.

The former US Assistant Secretary of State for Middle Eastern Affairs, Richard Murphy, told BBC News Online: "These are valid concerns, and I believe they are ones that the US must take very seriously. I believe one must plan not just for the disappearance of the regime but for what takes its place and what happens the day after."

Mr Murphy says that the US and others will need to help rebuild Iraq's economy and infrastructure after the ravages of more than 10 years of sanctions and the "wasting of the treasures of Iraq in the hands of its leaders".

Saddam Hussein has resisted many challenges to his rule

"It is not clear to me that this has been thought about by the administration as systematically and carefully as it needs to be, which would be irresponsible," Mr Murphy warns.

Not everyone agrees. Mustapha Alani, a Middle East analyst with the Royal United Services Institute in London believes the fears of Iraq's disintegration are overrated.

"I think the time for this has already passed," he said. "The Kurdish region is already heavily influenced by Turkey, but they don't want this area to be an independent entity - maybe autonomous, but not independent."

"In the south of Iraq, people want more of an influence on the centre of power - they are not interested in an independent state," Mr Alani argues.

Ineffectual opposition

Several commentators on Iraqi affairs have remarked that the Iraqi opposition groups in exile are so divided that their Western backers spend more time and money trying to unite these factions than trying to depose Saddam Hussein.

Mr Bush is accused of not planning for the period after Saddam Hussein

Washington has been seeking an alternative leadership for Iraq since 1990.

In 1998, the Clinton administration published the Iraq Liberation Bill, which formalised the ambition to depose Saddam Hussein and dedicated funds to backing opposition groups inside and outside Iraq.

Mustapha Alani is sceptical about the strength and influence of the opposition groups.

"They have turned out to be very weak and ineffective and to have no credibility at all. I don't think that Washington is very much concerned with what might happen after Saddam is toppled. I think they believe that the event will produce a pro-American regime, and that there is no real possibility of an anti-American one."

Mr Alani warns that the US is not going to find ready-made and active allies in Iraq as they did in Afghanistan - except for the Kurds. Saddam Hussein's Iraqi opponents operate outside the country.

"Iraq is a completely different environment from Afghanistan and the opposition is simply not strong enough," said Mr Alani.

Iraq's military

Due to the lack of viable opposition forces, Iraq's army is being seen as more and more important in plans to overthrow Saddam Hussein.

Over the years, there have been numerous reports of plots within the Iraqi military to overthrow Saddam Hussein which have been brutally put down.

Kurdish fighters may not be ready to respond to a US call to arms

Reports say senior army posts are rotated regularly, army units stationed near Baghdad have no ammunition in their guns and only a tiny number of people know about the president's whereabouts and movements.

Iraq's highly efficient and all-pervasive security services are dominated by Saddam Hussein's family.

The security services are believed to have been responsible for the deaths of thousands of Iraqis and to have kept a very tight rein on the army.

Senior army officers, who by Iraqi standards have privileged lives, have so far repaid the president with their loyalty.

Many of them would fear for their lives and their privileges if Saddam Hussein fell.

Washington has recently courted several former Iraqi army officers who have defected, with the hope that they could command the military after Saddam Hussein and avoid chaos in Iraq.

The most prominent of these, and least tainted by association with the current regime, is General Naguib Salihi.

However, General Salihi appears to have little ambition for political leadership and thinks the military should not be directly involved in politics.

Sad history of uprisings

There is very little chance of Saddam Hussein being swept away by a popular uprising and being replaced by a representative government.

In 1991, Iraqis in the north and south rebelled partly in response to US urgings.

Thousands were killed when the US failed to give these uprisings any backing and they were crushed by the Iraqi army.

In 1995 and 1996, CIA-sponsored rebellions in northern Iraq were put down by Saddam Hussein when US air cover failed to materialise.

After these experiences, Iraqi factions that might oppose Saddam Hussein are unlikely to respond to another American call to arms.

Occupation plan

One possible answer to accusations that Washington is not planning for the period after Saddam Hussein is a plan being floated for the military occupation of the country.

Under this plan, Iraq would be governed by an American military commander - much as Japan was governed by General Douglas MacArthur after its surrender in 1945.

US commanders would be responsible for maintaining stability and overseeing the transition to a democratic government for an undetermined period of time.

The plan would allow the US forces full control over Iraq while they find and destroy weapons of mass destruction.

One prominent Iraqi opposition figure told the BBC the Americans would be naive to attempt to occupy the country - though a temporary foreign presence working with an Iraqi civilian government would be acceptable.