The Ulster Unionists are to be shown the text of proposed legislation next week which will provide for the suspension of the Northern Executive if IRA decommissioning fails to take place.
This emerged following the launch by the Taoiseach and the British Prime Minister of a joint initiative designed to ensure the full implementation of the Belfast Agreement with the establishment of new institutions, including a devolved government.
The legislation is part of the "failsafe" mechanism aimed at reassuring unionists who are concerned that the IRA would try to hold onto its weapons even after Sinn Fein had taken its place in government.
The Assembly will be suspended if the joint Irish/British plan to resolve the impasse over decommissioning and the formation of the executive is not accepted within a fortnight, the Taoiseach said last night.
"The parties might seek clarification and we will try to give them that. But if people want to rewrite it or put a different interpretation on it, that won't happen," he said.
Meanwhile, the Sinn Fein representative to the decommissioning body, Mr Martin McGuinness, is expected to be replaced by a senior IRA figure who will discuss the modalities of disposing of weapons with General John de Chastelain.
Authoritative sources close to republican thinking said there was a "definite commitment" on the part of the IRA to decommissioning provided all the aspects of the Belfast Agreement were being implemented.
In the unionist camp, dissidents said they would be watching carefully for any shift by Mr Trimble from the official party policy of "no guns, no government".
Mr Ahern, meanwhile, emphasised that the Sinn Fein leadership would have a difficult job persuading republicans to accept the deal. He added: "Nobody should underestimate the really difficult task that Gerry Adams and his colleagues have. It is as difficult as that faced by David Trimble."
A meeting of UUP party officers is scheduled at their headquarters in Belfast's Glengall Street this morning and there may be a move there to call a meeting of the party executive to discuss the Blair-Ahern initiative.
Contrary to widespread speculation, a Trimble aide and a number of his parliamentary and assembly colleagues insisted that he would not call a special meeting of the 800-strong Ulster Unionist Council (UUC), the party's governing body, to seek its endorsement of the Blair-Ahern plan.
The Irish Times understands that at a crucial stage of the negotiations on Thursday night, Mr Trimble indicated to Mr Blair that he would be prepared to go to the party provided the deal on paper satisfied his requirement for a clear commitment to IRA decommissioning, and a sanction exclusively against Sinn Fein, should the IRA fail to deliver.
However it is understood that, late yesterday afternoon, a number of Mr Trimble's allies warned him that a decision to seek the support of the UUC could fatally split his party.
"David Trimble is saying he hasn't bought into this but if he decides to sell what he is currently describing as unfair, that raises questions over his credibility and his future," dissident unionists said last night.
Should the UUP leadership advocate acceptance of the Blair-Ahern document, which contradicted the party manifesto, dissidents said the required 60 signatures would be produced so that the issue could be thrashed out at the UUC.
This would be "the last great debate of this process" within the UUP and would end up in a split or a change of leadership.
In their joint statement, entitled The Way Forward, the two prime ministers proposed the nomination of ministers on July 15th with a devolution order being laid before the British parliament next day.
Meanwhile, the decommissioning body would have urgent discussions with the "points of contact" agreed by paramilitary groups. Decommissioning would start "within a specified time" and there would be three progress reports, in September, December and next May.
If commitments on decommissioning or a devolved executive were not met, the governments undertook to suspend the operations of the institutions set up under the agreement, principally the executive.
The failsafe legislation Seamus Mallon of the SDLP. It is likely to be the focus of debate in the coming fortnight. Mr Blair told the UUP assembly team on Thursday night that they would have sight of the text within a week.