US President George Bush has told the UN General Assembly the US-led invasion of Iraq was the right thing to do - but has come under fire for taking action without specific UN authorisation.
The UN debate comes as attacks continue in Iraq
Iraq was now free "because a coalition of nations acted to defend the peace - and the credibility of the United Nations", President Bush told the UN General Assembly.
But UN Secretary General Kofi Annan - and French President Jacques Chirac - implicitly rebuked the US for taking unilateral, pre-emptive action and called for the body to play a "full part" in rebuilding Iraq.
Pre-emptive attacks "could set precedents that resulted in a proliferation of the unilateral and lawless
use of force, with or without credible justification", Mr Annan said.
A year ago, President Bush told the same UN assembly that it had to deal with Iraq or risk the UN becoming irrelevant.
Now there are mounting concerns that the US military is getting bogged down in a widening guerrilla war in Iraq, hampering reconstruction efforts.
But the president urged the UN to put divisions over the war in Iraq behind it and "move forward" with stabilising and rebuilding the scarred country.
"Now the nation of Iraq needs and deserves our aid and all nations of good will should step forward and provide that support," he said.
But the BBC's Rob Watson, in New York, says there was little applause for Mr Bush's words, with the speech falling decidedly flat.
And in a report coinciding with the meeting, UN food agencies said several million Iraqis remained desperately hungry despite a better cereals crop and the lifting of economic sanctions.
The UN's Food and Agriculture Organisation and the World Food Programme said nearly half of Iraq's 26.3 million people were estimated to be in need of humanitarian aid.
French join criticism
America is seeking a Security Council resolution authorising the multinational force, and approving the US-appointed Iraqi Governing Council. The resolution would also let Iraqis help set the timetable for creating democratic institutions.
Mr Bush said the UN could "contribute greatly to the cause of Iraqi self-government", but he did not see the need for a greater UN role in Iraq.
Chirac also weighed in with an attack on US unilateralism
"As in the aftermath of other conflicts, the United Nations should assist in developing a constitution, training civil servants, and conducting free and fair elections," he said.
And the White House has flatly rejected French proposals for the early handover of power to Iraqi politicians, describing them as unworkable.
French President Jacques Chirac, who led diplomatic opposition to the invasion of Iraq, also joined criticism of the US in his speech.
"The war, launched without the authorisation of the Security Council, shook the multilateral system. The
United Nations has just been through one of the most grave crises in its history.
"No one should assign themselves the right to use force unilaterally and pre-emptively. No one may act alone," he said.
Mr Annan said the logic of unilateral, pre-emptive action represented a challenge to the principles the UN was founded upon.
But he said he was establishing a "high-level panel of eminent personalities" to examine current challenges to peace and security and recommend ways the United Nations could reform its institutions.
Mr Bush also used his speech to appeal for a worldwide drive to stop the spread of weapons of mass destruction.
But he mentioned neither North Korea nor Iran by name - two nations that his administration has accused of trying to build nuclear weapons.
"The deadly combination of outlaw regimes, terror networks and weapons of mass murder is a peril that cannot
be ignored or wished away," he said.
Mr Bush said that democracy in Iraq could be an inspiration to other countries in the Middle East.
Calling on the Palestinians to follow the course now under way in Iraq, Mr Bush said - in an apparent reference to Yasser Arafat - "the Palestinian cause is betrayed by leaders who cling to power but are feeding old hatreds and destroying the good will of others".
In other matters, Mr Bush also called for decisive action against HIV/Aids and for action to stop the spread of trading in sex slaves.
Mr Bush's speech is the centre point of a two-day visit to New York by the US president.