Tony Blair will urge George Bush today to return to diplomacy once the war on Iraq is over and give the United Nations an important role in post-Saddam reconstruction.
The Prime Minister will deliver his message when the American President flies into Belfast for a summit to discuss the military campaign, the Middle East peace process and the future of Northern Ireland.
More hawkish members of the Bush administration are determined to limit the UN's role to humanitarian aid as Iraq is run first by an American military administration and then by an interim Iraqi-run government.
But Mr Blair is determined to persuade Mr Bush to seek a new Security Council resolution giving UN endorsement and authority to the planned Iraqi Interim Authority (IIA).
Mr Blair's official spokesman said yesterday there was "no doubt" that the UN should have a role and stressed that "the more we have an international involvement, the smoother will go the reconstruction effort".
However, Downing Street and other ministers toned down comments made by Peter Hain, the Welsh Secretary, over his claim that the UN should be "in charge" of arrangements after the initial American-led transitional phase.
Mr Hain told The Sunday Telegraph that such a move was "essential" to efforts to open up the huge potential for European aid and development assistance. "What is crucial is that the UN is put in charge after the interim transitional arrangements," Mr Hain said. "That is vital to us and the whole of the European Union."
But Mr Blair's spokesman pointed out that Kofi Annan, the UN secretary general, had himself said that his organisation did not want to run the country. "The UN itself doesn't envisage having the capacity to do that. The UN wasn't in charge in Afghanistan. But the UN will have a role, of that there is no doubt," he said.
When asked if there were differences with the US, the spokesman said: "We want to continue to develop our thinking in tandem with each other. What's important is that we are continually across each others' thinking on that."
The precise role of the UN on the ground in the interim Iraqi authority is subject to intense debate between Britain, the US, France, Germany and Iraqi exiles.
Downing Street pointed to the joint Anglo-American statement in the eve-of-war Azores summit on 16 March that made clear a need for a new UN resolution.
When Mr Blair met the American President at Camp David last month, the Prime Minister said it was "premature" to discuss post-Saddam reconstruction. But with the war going well, it is understood the UK is now determined to ensure the peace can be used to rebuild damaged US-European relations.
Britain has accepted that Jay Garner, a former American general, and his Office of Reconstruction and Humanitarian Assistance, will govern Iraq for at least 90 days after the conflict ends.
But Mike O'Brien, a Foreign Office minister, stressed that any Americans working with the IIA would be there as "advisers", while Iraqis would take the decision-making ministerial posts.
In his first clear foray into the Northern Ireland peace process, Mr Bush will join the Prime Minister; the Taoiseach, Bertie Ahern, and the leaders of the three main pro-Good Friday Agreement parties during his two-day visit.
In Northern Ireland terms, the visit to Belfast is viewed as an encouragement to local parties to go the final mile in negotiations aimed at restoring the Northern Ireland Assembly, which are drawing to a close after many months.