Thousands of anti-war protesters are expected to demonstrate just outside Hillsborough, Co Down, this evening as President Bush holds his war summit with Mr Blair.
The Irish Anti-War Movement says it expects several thousand activists to travel from the Republic. A similar number is expected from Northern Ireland. Organisers say "three or four" buses will leave from Liberty Hall in Dublin at 1.30 p.m. and transport is also being arranged from Galway.
The anti-war coalition has strongly condemned the decision by Sinn Féin and the SDLP to meet President Bush.
While expressing unease about the war summit taking place at Hillsborough, the SDLP and Sinn Féin have both refused to boycott meeting President Bush and Mr Blair tomorrow for discussions on the peace process.
"All parties . . . should boycott this meeting with Bush and not be used as propaganda pawns to bolster his image," said the IAWM chairman, Mr Richard Boyd Barrett.
The village of Hillsborough will be sealed off to everyone but residents during the president's two-day visit.
The Northern Ireland Office said the media would have no access to the village due to "security considerations". Journalists will be based about three miles down the road at Sprucefield.
President Bush will fly into Belfast International Airport this evening. He will travel to Hillsborough Castle where he will be welcomed by Mr Blair. Anti-war protesters will most likely hold their demonstration at Sprucefield roundabout.
Ms Goretti Horgan of the North's anti-war coalition, said: "We have had only 48 hours to organise a demonstration in the middle of nowhere but such is the anger against Bush's war that we are expecting thousands of people to turn out."
She added: "The SDLP and Sinn Féin have public anti-war positions yet they are taking part in this charade. If they refused to meet Bush, it would send a very strong message around the world. Instead, they are trying to have it both ways. It won't wash."
Former Sinn Féin election worker Mr Frankie McMenamin said he would not vote for the party in next month's Assembly elections because it refused to boycott the Hillsborough meeting.
"I am one of many Sinn Féin supporters who believe our leaders should not meet Bush and Blair while they are prosecuting a war which is killing thousands of Iraqi people. Bush is polluting Irish soil by even standing on it."
Meanwhile, gardaí in Dublin are investigating a paint and graffiti attack on the beauty salon operated by Ms Celia Larkin, the Taoiseach's partner. Red paint was thrown on the windows of the shop on the Lower Drumcondra Road and anti-war messages were stencilled on the exterior.
Mr Boyd Barrett condemned the attack as "inappropriate".