The war launched in March 2003 with missiles striking Baghdad to oust President Saddam Hussein closes with a fragile democracy still facing insurgents, sectarian tensions and the challenge of defining its place in an Arab region in turmoil.

As US soldiers pulled out, Iraq's delicate power-sharing deal for, Sunni and Kurdish factions were already under pressure. The Shi'ite-led government asked parliament to fire the Sunni deputy prime minister, and security sources said the Sunni vice president faced an arrest warrant.

The final column of around 100 mostly US military MRAP armoured vehicles carrying 500 US troops trundled across the southern Iraq desert from their last base through the night and daybreak along an empty highway to the Kuwaiti border.

Honking their horns, the last batch of around 25 American military trucks and tractor trailers carrying Bradley fighting vehicles crossed the border early on Sunday morning, their crews waving at fellow troops along the route.