The full Cabinet from Dublin and most ministers from the new Northern Ireland Executive will attend the inaugural meeting of the North-South Ministerial Council in Armagh today.
This morning's meeting, which takes place at the Palace Demesne, formerly the residence of the Church of Ireland Archbishop and now the offices of Armagh City and District Council, is scheduled to last about 90 minutes.
In deference to unionist sensitivities, there is unlikely to be a group photograph, although, as with the first meeting of the Northern Executive, the cameras are likely to be admitted to the start of the meeting.
Political insiders said that at today's meeting the Ulster Unionist Party ministers, Mr David Trimble, Sir Reg Empey, Mr Michael McGimpsey and Mr Sam Foster, would "play a full part without going overboard".
The Taoiseach, Mr Ahern, in particular, had been made fully aware of the potential difficulties which today's meeting could cause for the UUP leadership. Mr David Trimble is likely to stress the modest scope of the implementation bodies and point out that they were set up for reasons of practicality rather than as part of an agenda to achieve a united Ireland.
Ten of the 12 Northern ministers will be there - the two Democratic Unionist Party ministers, Mr Peter Robinson and Mr Nigel Dodds, are refusing to take part.
Opening a new chapter in relations between the two parts of Ireland, the council was set up under the Belfast Agreement to allow Ministers from North and South to meet regularly, both on a plenary and one-to-one basis, for consultation, co-operation and action on matters of mutual interest throughout the island.
The new North-South Ministerial Council is loosely based on the European Union model whereby member-states deal with matters of common concern in the EU Council of Ministers.
Six implementation bodies are being established to carry out agreed policies, on an all-island and cross-Border basis. Six areas of cross-Border co-operation between existing agencies have also been agreed.
There was some concern in UUP circles last night at the prospect of its four ministers being outnumbered by over 20 nationalists.
However, today's meeting will be followed by the inaugural session of the British-Irish Council in London on Friday, where United Kingdom ministers will form a majority.
The meeting will formally establish the six cross-Border implementation bodies.
These will operate in the areas of inland waterways, food safety, trade and business development, European Union programmes, aquaculture and marine, and languages (Irish and Ulster-Scots or Ullans).
The council will also approve locations in both parts of the island for headquarters or suboffices of these bodies.
In addition, boards to administer or advise four of the implementation bodies are expected to be approved. The remaining two - EU programmes and inland waterways - will be run on an inter-departmental basis.
Consultation between Dublin and Belfast on the make-up of the new boards was continuing as late as yesterday.
The boards will be made up of equal representation from North and South. The Armagh meeting will also formally adopt the areas of North-South co-operation agreed under the terms of the Belfast Agreement.
A limited company to advance co-operation in tourism on a North-South basis is to be established, with its headquarters in Dublin.
A plenary session of the Northern Ireland Assembly takes place tomorrow afternoon when two new junior ministers in the office of the First and Deputy First Minister are due to be selected.
Mr Dermot Nesbitt is expected to take over an economic role, while the favourite for the post of junior minister for equality is the SDLP's Mr Alex Attwood.