US President George Bush is today expected to urge the IRA to fully disarm.
Mr Bush will call for an abandonment of all forms of paramilitary activity in his speech at the annual St Patrick's Day celebrations at the White House for political leaders from Belfast and Dublin.
The reception was taking place four days before the Irish patron saint's day on March 17th, in a move that reflects the way the Iraq crisis has overshadowed the issue of Northern Ireland in Washington.
The Ulster Unionist leader, Mr David Trimble, who is in the United States on a week-long visit, has urged Mr Bush to deliver a "blunt, unequivocal" message to Irish republicans.
"If Sinn Fein and the IRA fail this final test, then the US should reconsider its approach to them," he said.
But Sinn Féin has said progress towards restoring Northern Ireland's power-sharing Executive can be made during the get-together. "All of these occasions play their part in bringing people together," said party chairman Mr Mitchel McLaughlin.
The Taoiseach, Mr Ahern, who opposes an invasion of Iraq without full UN backing, this week rejected calls from Irish anti-war campaigners to boycott the ceremony to protest at America's war preparations.
He said although he disagreed on the issue of Iraq, he respected the Bush administration and would not "insult" it by staying away.
Mr Trimble, Sinn Fein leader Mr Gerry Adams, SDLP leader Mr Mark Durkan, Mr Daniel Ford of the Alliance Party and Ms Monica McWilliams of the Women's Coalition were also expected to attend the reception.
PA