Television messages recorded by Tony Blair and George Bush have been broadcast to the Iraqi people on Thursday.
Blair told Iraqis that Saddam, not them, was the coalition's target
Downing Street said the messages, recorded during their summit in Northern Ireland, were among five hours of daily broadcasts by the coalition's new "Towards Freedom" TV channel.
The broadcast came as Mr Blair warned victory was not yet complete in Iraq, after scenes of joyful Iraqis celebrating in Baghdad.
Foreign Secretary Jack Straw told MPs the "shocking truth" of Saddam Hussein's brutal regime was only now being exposed.
Mr Blair's official spokesman said some of "Saddam's people" still posed a threat although they were "melting away" in many areas.
The new channel would be the first opportunity for Iraqi people to get news free from Saddam's control, said Mr Blair's spokesman.
Eighty percent of the daily broadcast is US-produced, with one hour a day of UK Foreign Office material.
The broadcasts will come from America's flying broadcast station on a converted troop carrier plane named "Commando Solo."
It is part of coalition attempts to "underline to the Iraqi people why this is happening and what our intentions are for their country", a government spokesman said.
In the first broadcast, President Bush stressed the "clear and limited goals" the coalition had before Iraq moved to democratic rule.
The prime minister explained to Iraqis that Saddam Hussein, not them, was the coalition's target.
"This is the first time many of them will have heard this. It is important they understand our intentions," said the spokesman.
In a Commons statement on Thursday, Mr Straw said there was "understandable euphoria" but said hostilities were not yet at an end.
He said coalition forces would "do all they can" to secure towns where looting has broken out.
The government may send police advisers to help British forces maintain order, he said.
"We have taken on new responsibilities for the people of Iraq and we will apply the same energy and commitment to fulfilling those responsibilities as we have to the military task," he said.
But he also had a warning for Syria, urging it to "make a decisive break with the past and so contribute to a better future for the entire region".
He welcomed the appointment of a UN special adviser to work on issues including new resolutions for a post-conflict administration.
Mr Straw also pledged to rid Iraq of weapons of mass destruction.
Defence Secretary Geoff Hoon suggested the first parts of the interim authority headed by retired US general Jay Garner could be "in place in days".
Mr Hoon said it would be established in southern Iraq and small-scale conferences held to demonstrate Iraqis were in control of their particular areas.
Later, the prime minister paid tribute to Abdul Majid al-Khoei, the leading Islamic cleric assassinated in the southern Iraqi city of Najaf.
Mr Blair, who had met Mr al-Khoei a number of times in London, said he had been "saddened and appalled" by his death.
"He was a religious leader who embodied hope and reconciliation and who was committed to building a better future for a better Iraq."
On Thursday evening, Mr Straw met his Kuwaiti counterpart in London for talks on post-war Iraq and he will fly to the Gulf next week.
Foreign Office Minister Mike O'Brien will also travel to Syria and Iran, who fear they could become American targets in future.