The US has formally handed over power in Iraq, two days ahead of schedule.
Bremer (right) described himself as "ex-administrator"
At a low-key ceremony in Baghdad, US administrator Paul Bremer transferred sovereignty to an Iraqi judge, before leaving the country by plane.
Iraq's interim Prime Minister Iyad Allawi, who also took part in the ceremony in the heavily-guarded Green Zone, said it was "a historic day".
In a more colourful ceremony hours later, Mr Allawi and his cabinet ministers were officially sworn in.
But even this oath-taking was held in secret.
The transfer was widely welcomed - the European Union and the Nato alliance both pledged their support for Mr Allawi's government.
US President George W Bush said coalition troops would remain in Iraq as long as the country needed them and the government had requested their presence.
He said the security situation in Iraq was "tough" - and Mr Allawi's government had to take strong measures against the "brutal, cold-blooded killer" Abu Musab al-Zarqawi, an al-Qaeda suspect said to be behind many anti-coalition attacks.
Later US Ambassador John Negroponte arrived in Iraq to head what will become the world's largest embassy.
UK Prime Minister Tony Blair said the day was "an important staging post" for the future of Iraq.
Mr Blair said Iraq was a frontline in the battle against terrorism.
The BBC's world affairs editor John Simpson in Baghdad says bringing the handover forward was a clever tactical move that wrong-footed the Iraqi resistance.
However, he says it actually underlines the US-led coalition's big failure - its inability to stop the violence.
During the handover ceremony, Mr Bremer, describing himself as ex-administrator of the Coalition Provisional Authority, said the US-led coalition had come to liberate Iraq - as anyone who saw the mass graves left by Saddam Hussein could attest.
After formally taking office, he said the transfer of power was a "massive victory" for the forces of good in Iraq.
The Iraqi government still needs US-led forces to fight insurgents
"I call on our people to stand united to expel the foreign terrorists who are killing our children and destroying our country," Mr Allawi said in a televised address.
He said the government's programme would be announced in the next few days - it would build a society for all Iraqis, irrespective of ethnicity, colour or region.
Our world affairs editor says now the interim government has taken over the job of trying to restore order, Mr Allawi knows he will be judged according to his success or failure.
Mr Bush and Mr Blair - apparently the only leaders at the Nato summit aware that the handover was taking place - exchanged smiles and a brief handshake after consulting their watches.
But the surprise move was first disclosed by Foreign Minister Hoshyar Zebari, speaking after talks with Mr Blair at the summit.
Will the new authority be legitimate?
Nato leaders endorsed a plan to help train Iraqi security forces.
The move followed an urgent request from Mr Allawi.
It is not yet clear when the training operation will begin, nor how many personnel will be involved.
French President Jacques Chirac told reporters the training would happen outside Iraq - and would be mostly done on a bilateral basis.