The US and the EU have pledged strong support to the new Iraqi government ahead of the 30 June transfer of power.
It was President Bush's first official visit to Ireland
The leaders issued a joint statement at the end of a summit in Ireland saying Baghdad needed the world's backing if Iraq was to become a democratic nation.
The move shows that the US and European nations have set their disagreements on Iraq aside, correspondents say.
The summit also covered trans-Atlantic trade issues, the crisis in Sudan and Iran's nuclear programme.
The situation in Iraq just days before the scheduled handover dominated the brief summit at Dromoland Castle, in County Clare - the first between the US and the EU since the latter's expansion to 25 members in May.
"The bitter differences over the [Iraq] war are over," Mr Bush said during a joint news conference with Irish Prime Minister Bertie Ahern and outgoing European Commission President Romano Prodi.
In their joint declaration on Iraq, the EU and US said they would:
- support the UN's role in rebuilding Iraq and holding elections no later than 31 January 2005
- pledge to reduce Iraq's $120bn foreign debt
- offer to help train Iraqi security forces to deal with the continuing violence
Mr Ahern said the summit reaffirmed the strength, depth and significance of the trans-Atlantic relationship, which he said was "based on a common set of democratic values".
Earlier, Mr Ahern - whose country holds the rotating EU presidency - used bilateral talks with Mr Bush to express "abhorrence" at the recent abuse of Iraqi prisoners by US troops.
Relations between the US and the bloc have been damaged by differences over the Iraq war and Middle East conflict.
But the BBC's Kevin Connolly says the EU and the US used the summit to draw a line under disputes about the rights and wrongs of how and why the war was fought and to begin focusing on the future.
Observers say shoring up international support for the US presence in Iraq is a goal of the Bush administration, which faces presidential elections in November.
Domestic opinion polls show declining support for the Iraq occupation, as a succession of deadly bomb attacks overshadow the planned transition of power.
Protests and deals
In other agreements, the EU and US condemned Iran's plans to resume production of centrifuge parts and urged Tehran to "rethink its decision".
The leaders also called on Sudan to deal with government-backed Arab militias who have driven tens of thousands of African villagers from their homes in the western Darfur region.
Protesters were kept well away from the summit venue
And a deal was signed to make the EU's planned satellite navigation system compatible with the existing US Global Positioning System.
The summit was held amid tight security, with about 4,000 police and 2,000 soldiers - a third of the Irish security forces - being deployed to protect Mr Bush and the EU leaders.
As talks got under way, about 1,000 protesters marched up to the security cordon of the summit venue.
President Bush later flew to Turkey to attend a two-day summit in Istanbul which starts on Monday.
Before leaving Ireland, he said "Nato has the capability and... the responsibility to help the Iraqi people defeat the terrorist threat facing their country".
In Istanbul, Nato heads of states are expected to approve an initial agreement reached by the alliance's ambassadors to help train Iraq's security forces.
The initial deal was hammered on Saturday following an urgent request from the country's interim Prime Minister Iyad Allawi.
"I am confident here in Istanbul we will give the final approval," Nato Secretary General Jaap de Hoop Scheffer said.
The summit will also discuss the alliance's work in Afghanistan, where Nato has a contingent of peacekeeping troops.