The Ulster Unionist Party leader, Mr David Trimble, will warn the Taoiseach, Mr Ahern, in Dublin today that without modification of the Patten proposals on police reform and in the absence of decommissioning, the Belfast Agreement could collapse.
Sinn Fein in turn has insisted that the Police Bill as currently framed fails to meet the promise of Patten to create a force to which nationalists could pledge alliance.
Mr Trimble, the North's First Minister, is due to meet Mr Ahern on the margins of today's North-South Ministerial Council meeting in Dublin Castle, where he will advise him that the pro-agreement wing of the UUP is under increasing pressure following last week's loss of the South Antrim Westminster seat to the DUP.
Mr Trimble provided a similarly gloomy analysis of the political situation when he addressed a fringe meeting at the Labour party conference in Brighton yesterday evening. He focused on the Patten proposals, which he said caused "deep offence" to unionists, and appeared to be designed "for nationalists only".
"Unionists who might have become reconciled to the agreement, having seen the benefits with the administration up and running, are now so offended and worried about the treatment of the police and the potential for its corruption by paramilitary influence they are prepared to vote down the agreement. That is a very serious development," he said.
"The Ulster Unionist Party has made sacrifice after sacrifice, taking huge risks to move the process forward for the betterment of Northern Ireland. But others have got to realise now that it could be lost because of Patten and the absence of decommissioning," added Mr Trimble.
The Sinn Fein president, Mr Gerry Adams, last night warned that "republicans will not accept their rights being dictated by what is or is not acceptable to unionism. The flaw in the British government approach seems to be that it measures its delivery of the agreement on how it affects Mr Trimble."
And speaking earlier at the launch of a Sinn Fein document on the Police Bill at Stormont, Mr Adams said the constituency Sinn Fein represented deserved a new police service.
"What Patten envisaged was the transition from a paramilitary, unrepresentative police force - a unionist militia - to a representative, democratically accountable policing service - civic policing - which enjoys the support of the community as a whole. This is what the Good Friday agreement requires," said Mr Adams.
Among the many points in the Sinn Fein document were arguments that the Police Bill assigned excessive policing powers to the Northern Secretary and police chief constable, and that it limited the power of the Policing Board, the Police Ombudsman and the Oversight Commissioner.
