But he was also being briefed about the problems facing the Stormont administration, including the transfer of policing and justice powers from London and continued existence of the IRA Army Council.

The President was fulfilling a promise to come to Northern Ireland to demonstrate his personal support for power-sharing devolution, at the end of a six-day farewell tour of Europe.

Accompanied by First Lady Laura Bush, who was in the province for the first time, Mr Bush was due to hold a series of meetings at Stormont with First Minister Peter Robinson, Deputy First Minister Martin McGuinness, Taoiseach Brian Cowen and the Republic's President Mary McAleese.

A spokesman for Mr Cowen said the meetings would focus on recent political progress but also review outstanding political issues and analyse how best to build on the recent international investment conference.

Mr Bush was also joined by Prime Minister Gordon Brown after formal talks between them in London this morning.

No major speeches or announcements were being scheduled during the expected five-hour visit to the province, which was also due to focus on American backing for integrated education.

The President's visit was also due to include a little piece of American culture already imbedded in the province — a cross-community basketball project — funded from the United States.

As the trip got underway, the generosity of American philanthropic investment in recent years was being pointed up by Ireland Funds Global which said more than £13m of US cash has been spent on key community integration projects since the Good Friday Agreement ten years ago.

While Mr Bush and his entourage were not expected to go into Parliament Buildings, the Assembly shut down business for the day — which was to have included Ministers Questions — with delegations from all the parties expected to meet the President briefly.

The Alliance Party said the shutdown, which also included a number of committee meetings, was "needless".

Due to the size of the security operations, the PSNI brought in a number of vehicles loaned from other forces in the UK. Officers placed a long line of crash barriers along the Upper Newtownwards Road near Stormont Buildings.

Even before he arrived Mr Bush was being asked to back victims of IRA violence and their relatives in a court case against Libya, being pursued through the American courts, relating to attacks where Semtex explosives were supplied by the regime of Colonel Gadaffi.

Michelle Williamson, who lost her parents in the Shankill Road fish shop bombing in Belfast 15 years ago, said: "It is important that George Bush backs us. We have been let down by our own Government."

The class action, supported by the Families Acting for Innocent Relatives group, is being taken in the American courts because the 180 claimants include a number of US citizens.

Meanwhile, a ring of steel was placed around Stormont as security was heightened in preparation for the visit of the US President.

Flying in from London on the presidential Airforce One, Northern Ireland was the final stop on his European farewell tour before leaving office in January.

The president, who also met Mr Brown yesterday for talks on Iraq and other issues, is expected to be greeted at Belfast International Airport by the Prime Minister, who, along with his wife Sarah, will travel to Aldergrove by government jet.

Mr Bush was said to have requested a meeting with Mr Paisley, with whom he struck up a rapport during last December's visit to Washington with Mr McGuinness when a scheduled 15-minute session stretched into more than an hour.

Bush is thought to want to put his seal of approval on devolution, having been invited to do so by the then DUP First Minister and Martin McGuinness during their White House visit last December.

Meanwhile, the First Lady and Sarah Brown are understood to have a separate programme to follow. After the Stormont audience, the US leader is scheduled to visit a local primary school, where he will be joined once again by the First Lady. The couple are expected to meet pupils and staff, where cross-community schooling is likely to one of the main topics of discussion.

Motorists were being warned to expect widespread traffic disruption today, and a helicopter exclusion zone will be in place in the skies above Belfast.

Bush's Belfast visit is nevertheless set to be marked by protests from anti-war campaigners unhappy at the reception for the architect of the wars in Iraq and Afghanistan.

Ahead of his visit, Amnesty International yesterday staged a demonstration to voice concerns about prisoner treatment and the detention of terror suspects. And today, two further protests were expected at City Hall and at Stormont, organised by the Bush Not Welcome Group and Belfast Anti-War movement.

Amid tight security controls, the Stormont estate is to be closed off for nearly 48 hours, and there will be flight exclusion orders over the city.