A further step in the process aimed at implementing the Belfast Agreement is expected to be taken today when the British government is due to announce details of how devolution of powers might take place.
The Northern Ireland Secretary is expected to issue a statement which, according to senior sources, will propose the nomination of ministers to the new executive on November 29th, two days after the special Ulster Unionist Council (UUC) meeting on Saturday next.
This would be followed by the formal devolution of powers, the first meeting of the new executive and the appointment of paramilitary representatives to meet the decommissioning body.
All these actions would take place the same day and would be quickly followed by the first meeting of the North-South ministerial council in Armagh and the inaugural session of the British-Irish council, probably in London. A statement from Dublin on the new councils is expected shortly.
Having issued the statement, Mr Mandelson will make a follow-up speech to the annual conference of the Northern Ireland Women's Coalition at Newcastle, Co Down which will be intended to support the UUP leader, Mr David Trimble, in his campaign to win over his party.
Meanwhile, the UUP leader will continue his drive in the media and at party meetings to win a comfortable majority at the UUC meeting, which is expected to be held in the Ulster Hall, Belfast.
Independent observers estimate the level of support for the deal in the UUC at 60-40 and Mr Trimble will need to maintain that support, if not increase it, to claim a convincing victory.
A news conference called by Mr Trimble to announce the forthcoming UUC meeting turned into an embarrassing wrangle when a leading opponent of the deal, Mr David Brewster, interrupted the proceedings to challenge the veracity of Mr Trimble's account of a party officers' meeting which they had both just attended.
Later, Mr Trimble and Mr Brewster issued a joint statement expressing regret over the incident and asking the media to "disregard the unfortunate exchange of comments."
The Northern Secretary, who has moved centre-stage in the peace process with the departure of Senator George Mitchell, is due to make a further statement in the House of Commons on Monday afternoon which sources said would outline how the twin aims of devolution and decommissioning can be achieved.
On the sensitive issue of decommissioning, Mr Mandelson will have the challenge of providing what sources called "the form of words that David Trimble is looking for", without alienating republicans.
Northern Ireland questions will be taken in the House of Commons on Wednesday next and may be used by some UUP MPs to express their opposition to the deal.
Mr Trimble suffered a setback yesterday when one of the two deputy whips in his Assembly party, Mr Derek Hussey, asked to be relieved of his duties on the grounds of opposition to the deal.
Speculation continues about the position of Mr John Taylor, seen as a critical figure in next Saturday's proceedings. The Strangford MP returned yesterday from a parliamentary visit to Iran but sources close to him said he would be talking to his constituents, meeting the party leader and updating himself on developments and would make no comment before Monday.