The Taoiseach, Mr Ahern, and the British Prime Minister, Mr Blair, will fly to Belfast this afternoon to begin a final, dramatic bid to save the Belfast Agreement. They will present a joint proposal to the Northern parties.
Mr Ahern and Mr Blair plan to propose the setting up of a Northern Ireland executive in exchange for explicit commitments from paramilitary groups to decommission their weapons by May 2000.
They intend to leave the political parties and government officials to consider the plan and to return to Belfast early next week.
But the sense of crisis deepened last night as the Ulster Unionists moved to pre-empt a report from the International Commission due next Tuesday, with a warning to Gen John de Chastelain that "euphemistic language" would not resolve the decommissioning deadlock.
Mr Ken Maginnis, the UUP's security spokesman, told The Irish Times that the general's questions to the parties tabled on Wednesday were capable of answer by Sinn Fein without moving the process forward, and "could actually be used by Sinn Fein to justify further delay in meeting its obligation to achieve decommissioning under the terms of the agreement." Speaking earlier, his party leader, Mr David Trimble, said an acknowledgement of the "obligation" to disarm would not represent significant progress.
Mr Ahern will meet Mr Blair at 10 Downing Street this morning before joining him at Cardinal Basil Hume's funeral at Westminster Cathedral. After the funeral they will travel to the North.
With just six days to go to the devolution deadline, the joint British/Irish approach to the negotiation is clear: to secure Ulster Unionist agreement to the creation of the power-sharing executive by next Wednesday, and to "stretch" the republican movement to give Mr Trimble "certainty" that decommissioning will be achieved within the time frame envisaged in the agreement.
However, it is understood there is as yet no understanding between the Prime Minister and the Taoiseach as to what, if anything, should happen if Mr Blair's "absolute" deadline is not met. And there were continuing signs last night of clear differences between London and Dublin over what might constitute "certainty of achievement" (of decommissioning) and what sanction, if any, could or should be directed at Sinn Fein should the IRA ultimately fail to deliver.
The latest indications are that Mr Blair's approach to the crisis is rooted in the proposal long-canvassed by the Deputy First Minister designate, Mr Seamus Mallon, to have republicans accept an "obligation" to decommission by May 2000, or have Sinn Fein excluded from the executive should the IRA fail to discharge it. This was being characterised in London as offering "the certainty of achievement, and the certainty of sanction if they don't do it".
However, it is widely believed Mr Mallon's plan, first mooted at the SDLP conference last autumn, finds no favour with his party leader, Mr John Hume. And key Irish players suggest the problem with any proposal for Sinn Fein's exclusion - as with the original unionist "pre-condition" for prior decommissioning - is that it does not accord with the terms of the agreement.
In the Commons on Wednesday Mr Blair insisted the acceptance of an inclusive executive, and "that there has to be decommissioning" were the "two essential foundation blocks" without which the agreement would not work.
British sources last night refused to be drawn on a number of key questions which arise. These specifically concern the start date for decommissioning in relation to the formation of the executive, and the point at which the proposed "sanction" might be invoked for non-compliance.