Bush will meet his main Iraq war ally British Prime Minister Tony Blair in Northern Ireland.

Rice is already in Moscow to start talks with President Vladimir Putin, a critic of the war who will require reassurances after an incident in which Russian diplomats fleeing Baghdad came under heavy fire, US officials said.

Secretary of State Colin Powell called his Russian counterpart Igor Ivanov, promising him that an investigation into the incident was underway, the State Department said.

The US-British summit in Northern Ireland will be the third in three weeks for the two leaders who embarked on the Iraq war without the United Nations' explicit approval and in defiance of opposition from France, Russia and Germany.

Bush and Blair differ over the role the United Nations should play in any Iraq without Saddam Hussein however.

The US national security advisor has dismissed strong calls from France, Germany and Russia for the United Nations to be responsible for running Iraq when the fighting finishes.

Rice said Friday that "having given life and blood to liberate Iraq," it was natural that the United States and Britain should take the lead in Iraq when the war is finished.

But Blair has also called for the United Nations to have a central role.

The prime minister has said Britain would seek fresh UN Security Council resolutions to guarantee Iraq's territorial integrity, ensure humanitarian aid quickly reached civilians in need and approve a post-war administration for Iraq.

Conscious of the international opposition to the Iraq war, Blair has also been instrumental in recent weeks in pushing the US leader to make a greater commitment to the Middle East peace process. This will also be discussed at the Northern Ireland summit.

Bush spoke with Russia's President Vladimir Putin on Saturday and the White House said Rice arrived in Moscow on Sunday to start meetings.

Rice, who is fluent in Russian, is to meet on Monday with Ivanov, Defense Minister Sergei Ivanov and Security Council chief Vladimir Rushailo, according to the Interfax news agency.

A US official, speaking to AFP on condition of anonymity, said Rice would also meet Putin before travelling onto meet up with Bush in Northern Ireland on Monday or Tuesday.

White House spokesman Taylor Gross said: "We're committed to our long-term strategic relations with Russia. We've been through some difficult times, and we look forward to exchanging views with the Russians on how best to move forward."

Russia has been attempting to tone down its outspoken criticism of the war in recent days, saying it did not wish to see a US defeat but has still joined France and Germany in making a strong call for a UN-backed administration in Iraq.

But Rice swept aside the European calls on Friday saying Iraq is a "unique" case.

"It would only be natural to expect that after having participated and having liberated Iraq with coalition forces, and having given life and blood to liberate Iraq, that the coalition intends to have a leading role," she said.

The United States plans to let a military administration under its main war commander, General Tommy Franks, run Iraq until an interim Iraqi administration can take over. But there have been divisions in Washington over the plans.

US Deputy Defence Secretary Paul Wolfowitz said Sunday the US military may have to run Iraq for more than six months after the war has finished before it hands over to an Iraqi authority.

Wolfowitz said it took six months to form a government in the virtually autonomous northern Iraq after the 1991 Gulf War. "This is a more complicated situation; it probably will take more time than that," he said.

"The reconstruction of Iraq, I think, is going to be one of the most important projects for the international community in many years. And the UN can be a mechanism for bringing that assistance to the Iraqi people.

"But our goal has got to be to transfer authority and the operation of the government as quickly as possible not to some other external authority, but to the Iraqi people themselves," Wolfowitz said.

SPACE.WIRE