BELFAST, Northern Ireland - President Bush and British Prime Minister Tony Blair began two days of talks here last night as they sought to bridge differences in their visions for a postwar Iraq, with the near-collapse of President Saddam Hussein's regime lending urgency to the deliberations.

Victories over Hussein's Republican Guard and a swift advance by U.S. forces into Baghdad appear to have sped up the timetable for the installation of an interim authority to lead Iraq until a permanent government takes shape. But Bush and Blair, who convened over dinner at a mansion outside Belfast, have been at odds over the role the United Nations should play immediately after the war. The issue has strained the close alliance between the two leaders, who are meeting for the third time in just over three weeks.

Aboard Air Force One, Secretary of State Colin L. Powell told reporters traveling with the president that Bush and Blair hope to release a joint statement today outlining proposed U.N. Security Council resolutions, which, if approved, would endorse a postwar reconstruction plan.

"There isn't as much debate and disagreement as you might read in the newspapers," said Powell, seeking to minimize any discord.

Powell said a team from Washington is to leave this week for the Persian Gulf region to join Defense and State Department representatives already in place to start laying the foundation for an interim authority to administer Iraq until a new government emerges.

"It is time for all of us to think about the post-hostility stage - how we create a representative government consisting of all elements of Iraqi society," Powell said.

Bush supports some role for the United Nations, primarily in the area of humanitarian aid, but insists that the United States and Britain - whose troops have done the fighting - play the leading role until a broad-based Iraqi government can take over.

Bush wants an interim governing authority - composed of Iraqi exiles and Iraqi leaders from within the country - to work in concert with a Pentagon-run agency that would secure the nation and provide most government services, even as fighting continues.

Blair favors a more substantial role for the United Nations, echoing European leaders who say the international body has greater credibility than the United States to run the country.

The British leader, though, has appeared to come closer to Bush's position. Last night, a Blair spokesman told reporters that the prime minister is not insistent on the United Nations leading the reconstruction effort. Still, he added, "There are practical, common-sense issues that have to be worked out" with Bush before moving forward.

The prospect of a U.S.-led occupation of Iraq could further strain relations with France, Russia and Germany, who have called for the United Nations to control Iraq after the war. Officials from these countries, as well as some members of Congress, say U.N. control would ensure a smoother reconstruction, with less anti-American protest in the region.

"U.N. involvement does bring legitimacy," U.N. Secretary General Kofi Annan said yesterday in New York, "which is necessary for the country, for the region and for peoples around the world."

Irish Prime Minister Bertie Ahern, who is to join the summit today, took a similar stance, telling reporters in Dublin: "We want to see a new administration that will have greater legitimacy if it is under the [authority] of the international community."

Blair is pushing for U.N. involvement in part to try to mend trans-Atlantic relations, which were damaged when France, Germany and Russia vehemently opposed war.

In addition to Iraq, the two leaders are expected to discuss their intention to release a "road map" for peace in the Israeli-Palestinian conflict.

Bush arrived here late yesterday under gray skies for his working dinner with Blair. Serving as their backdrop is a city that has seen violence for decades, as religious parties have fought over whether Northern Ireland should be aligned with Roman Catholic-dominated Ireland, or with Protestant Britain.

Northern Ireland is now controlled by London, but the Good Friday Agreement, signed in 1998, would allow Catholics and Protestants to share in a new government. This working-class city has slowly approached normality, with far fewer terrorist attacks. The checkpoints encircling the city and the military presence of the 1990s are gone. Prisons that used to house political prisoners sit empty.

But there are still security cameras at street corners, banners supporting paramilitary religious groups on the sides of buildings and routine bomb threats. One such threat forced the closure of a major highway and snarled traffic downtown only hours before Bush's arrival.

The president was to remain for the duration of his 25-hour stay at Hillsborough Castle. More English manor house than castle, the building lies 12 miles southwest of the city. Security near Hillsborough was tight, and protesters were not allowed near the president and prime minister. Riot police guarded the castle grounds.

The president, aides said, plans to support a proposal Blair might offer this week ensuring that the 1998 peace accord is carried out in full and a new assembly is seated.

Blair requested the meeting with Bush in Europe. The prime minister, when he joined forces with Bush on Iraq, suffered criticism at home and was portrayed as Bush's lackey. A meeting on Blair's turf shows the leaders on a relatively equal footing and stands to bolster the prime minister's image with British voters.

Former President Bill Clinton was intimately invested in the Northern Ireland conflict, working closely with Blair to end decades of violence that killed more than 4,100 people.

Bush has taken a mostly hands-off approach. Aides said he felt that now, as Blair seeks to make strides on the five-year anniversary of the Good Friday Agreement, was an appropriate time to get more involved.

After a one-on-one meeting in the morning and a brief question-and-answer session with reporters, Bush and Blair are to meet in the afternoon with Ahern and other political leaders from both sides of the Northern Ireland conflict.

The White House had an inauspicious run-up to Bush's visit. On Friday, spokesman Ari Fleischer said Bush would be visiting Dublin, which is not in Northern Ireland. He quickly apologized and said he was not a geography major.

Yesterday, White House aides distributed glossy media credentials for "The Trip of the President to Belfast, Ireland." Belfast is in Northern Ireland, and whether it may one day be incorporated into Ireland is the issue the two sides have been fighting over for more than 30 years.

A White House spokesman said of the error on the credential: "It's not a political statement. It's a typographical statement."