Mr David Trimble will arrive in Dublin this morning to assure the Taoiseach, Mr Ahern, that the Ulster Unionists seek suspension of the Executive and other governmental institutions in order to save the Belfast Agreement, and not as a precursor to withdrawal from the current process.
However Northern Ireland's First Minister will tell Mr Ahern that - barring a dramatic last gasp report from Gen. John de Chastelain confirming that the IRA would disarm, and when a decommissioning programme would commence - he and his colleagues will not continue in office.
Mr Trimble reinforced that message yesterday in separate meetings in London with the British Prime Minister, Mr Tony Blair, and the Northern Secretary, Mr Peter Mandelson.
The UUP's determination to force a conclusion on the issue tomorrow has also been made plain in discussions between Mr Mandelson and Sir Josias Cunningham, the president of the Ulster Unionist Council.
Sources confirmed that Mr Mandelson and Sir Josias have been in touch about "the orderly procedure to suspension or resignation [by Mr Trimble and his ministers]", assuming no further, conclusive report from Gen. de Chastelain.
Hopes for a further report from the general were kept alive by Mr Mandelson in the Commons yesterday, and again, last night, by the Minister for Foreign Affairs, Mr Cowen, after his meeting with the Secretary of State in London.
Senior Ulster Unionist Party members on all sides say they have no doubt Mr Trimble will implement his post-dated resignation if the suspension of the institutions is not effected tomorrow, unless there is an unexpected reversal of the republican movement's stated position on arms in terms which might be acceptable to the Ulster Unionist Council.
The legislation enabling the restoration of direct rule completed its stages in the House of Lords last night, and the Northern Ireland Bill 2000 is due to receive the Royal Assent this evening.
There is some uncertainty about the precise time at which Mr Mandelson might table the Order bringing suspension into effect tomorrow, amid speculation that the Taoiseach might yet fly to London for a final summit meeting with Mr Blair.
In anticipation of possible delays, it is understood arrangements have been made by the Ulster Unionists to ensure access to the Assembly's Presiding Officer at any point tomorrow.
In any event, sources say Sir Josias is determined that "suspension or resignation" will need to have occurred before the Ulster Unionist Council meets in the Waterfront Hall at 10.30 a.m. on Saturday.
Following the meeting between Mr Mandelson and Mr Cowen, British sources stressed that the Northern Secretary did not want to suspend the institutions of government but understood "the dynamics of the time-scale" within which decisions would have to be made.
Having apparently been told there was no question of a postponement of the UUC meeting, one British source said: "We don't like it [suspension] either. Clearly it would be better avoided. But not at the price of losing David Trimble's position in the process."
During Northern Ireland Questions earlier yesterday, Mr Mandelson made an "eleventh hour" appeal to the IRA to respond "in a constructive way" on decommissioning.
He said: "Nobody is asking for surrender by the IRA. Nobody is asking for humiliation to be heaped on the IRA.
"I just say that if politics is to work, and if we are to see the decommissioning that is an essential part of the peace process, then there must be certainty . . . if confidence in all the institutions is going to be rebuilt."