Kofi Annan's comments came after a meeting with President George Bush in Washington on Tuesday that signalled improving relations between the UN and US.
"I have decided to send a team, a team that will go in to work with the Iraqis in finding the way forward. Everyone agrees that sovereignty should be handed over as soon as possible," Annan said in the White House Oval Office.
The UN chief did not say when the team would go to Iraq, where the US plans to transfer power to a provisional government named by a transitional assembly without holding national elections.
That blueprint has drawn mounting opposition from the Shia Muslim community in Iraq.
Emphasising the fence-mending nature of Annan's visit, Bush paid tribute to the world body he once derided as a "debating society" for denying its explicit backing to the US-led invasion of Iraq in March 2003.
"The world is changing to the better, and the United Nations is playing a vital role in that change," Bush said, stressing that he and Annan had discussed Iraq, Afghanistan, Pakistan, India, the Middle East, and Africa.
Iraqi Shia have been calling for
general elections to be held soon
Annan said that, after a year "all taken up" by divisions over the war, the US and UN were reaffirming the commonality of their interests, starting with efforts to rebuild Iraq.
"I believe that the stability of Iraq is in everyone's interest," said Annan. But he cited "some disagreement" over how to establish a provisional government and said his team would seek to overcome that hurdle.
The group will seek to convince Iraqis "that if they could come to some consensus and some agreement on how to establish that government, they're halfway there," he said during their brief joint public appearance.
Shia Iraqi leaders have urged a swift transition to a democratically elected government – which would favour their numerous followers. But the US foresees an iterim government of appointed delegates, saying Iraq is not ready for a general election.