There are more than 70 Iraqi opposition groups, spanning a broad spectrum of political views from Arab and Kurdish nationalists to Islamists, communists and monarchists.
Only four or five have any real credibility, and even these suffer from splits and rivalries and, in most cases, a lack of support inside Iraq itself.
The Iraqi National Congress (INC) - created in 1992 and based in London - considers itself the main umbrella group.
It is committed to the overthrow of Saddam Hussein and the creation of a democratic, pluralist Iraq.
The INC enjoys support in the American Congress and Senate and between 1992 and 1996 it operated in northern Iraq in co-operation with the CIA.
But in 1996 Saddam Hussein's forces destroyed its infrastructure in the north.
This - and a series of splits and defections - have seriously weakened its effectiveness.
The only groups firmly based on Iraqi soil are the two main Kurdish factions - the Kurdish Democratic Party and the Patriotic Union of Kurdistan.
They have run their own Western-protected enclave in northern Iraq since Saddam Hussein's defeat in the Gulf war of 1991. But they have been plagued by disunity.
The Clinton administration hosted a meeting in Washington in September which sought to end the feud between the KDP and PUK leaders.
They pledged to work together in a new power-sharing arrangement, but it is known that both groups maintain links with Baghdad.
The Iraqi National Accord - with offices in London and in the Jordanian capital Amman - contains many former army officers and intelligence officials.
It claims to have support within the armed forces and the ruling Baath Party.
Some policy-makers in Washington and London accordingly think it is better placed than other groups to overthrow or assassinate Saddam Hussein. Others suspect he has successfully penetrated the group and view it with mistrust.
In general the Iraqi opposition groups reflect the ethnic, religious and tribal divisions within Iraq.
Since the latest confrontation began the US and Britain have both pledged to increase their support for opponents of the Iraqi leader Saddam Hussein, and the UK government is encouraging 16 Iraqi opposition groups to settle their differences and work together for a democratic Iraq.
But apart from the Kurds, they lack a power base inside the country.
Most work in exile, either in London or in various Middle East capitals, including Amman, Damascus and Tehran.
But if they co-operate with Iraq's neighbours or with Western governments, they risk losing credibility with ordinary Iraqis - long accustomed to hearing their government denounce opposition figures as traitors in the pay of foreigners.
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Iraqi National Congress
Patriotic Union of Kurdistan
Supreme Council for Islamic Revolution in Iraq (based in Tehran)
Worker Communist Party of Iraq
Kurdistan Democratic Party-Iraq
Iraqi National Accord
Iraq Action Coalition
Iraq Net
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