Unionist opponents of the Belfast Agreement are considering a realignment which could lead to the creation of a new political party, The Irish Times has confirmed.
Sources say the possibility of a new party is entirely dependent upon developments inside the Ulster Unionist Party (UUP) and the Assembly over the coming months.
Well-placed sources said last night that breakpoint for Mr David Trimble and his internal opponents would come if he decided to sit in the new Executive with Sinn Fein without the decommissioning of IRA weapons.
Sinn Fein will be entitled to two seats on the Executive following the Assembly election.
A regrouping of the anti-agreement unionist forces would not easily be achieved, given the powerful personalities and competing claims of senior MPs like the Rev Ian Paisley, Mr Robert McCartney and Mr William Ross.
However, there is already speculation about the potential leadership roles of the leading dissident MP, Mr Jeffrey Donaldson, and Mr Peter Robinson, the deputy leader of the DUP, in the event of realignment.
Details of the latest threat to Mr Trimble's position emerged as Mr Donaldson, and fellow Ulster Unionist MP Mr William Thompson, signalled they would quit the party if Mr Trimble enters a Northern Ireland Executive with Sinn Fein without the prior decommissioning of IRA weapons.
In his most direct challenge to the party leadership to date, Mr Donaldson declared at the weekend:
"I could not support the Ulster Unionist Party sitting in the Executive, shadow or otherwise, with Sinn Fein/IRA in the absence of the decommissioning of their weapons, the complete end of their violence, and the progressive dismantling of their paramilitary organisation.
"If the party decides to sit in the Executive with Sinn Fein/IRA in those circumstances, I and many loyal party members would have to reconsider our position."
It is understood Mr Donaldson has not been directly involved in discussions with members of the DUP or the UKUP about a possible realignment, which would be designed to win the maximum number of Ulster Unionist defections - so fundamentally changing the arithmetic within the Assembly as to force a renegotiation of the Agreement.
And it is clear that a regrouping will not take formal shape while anti-Agreement campaigners, led by Mr Donaldson and his fellow dissident MPs, fight a rearguard action within the UUP to tie Mr Trimble to specific commitments about the party's attitude to Sinn Fein in the new Assembly and Executive.
However, sources privately say that - without significant movement by the IRA on decommissioning - they believe a formal split within the UUP is now inevitable.
The party's executive committee faces an acrimonious meeting this Friday, when the clash between pro and anti-Agreement members will be fuelled by the inquest into the collapse in its share of the vote, which left it trailing the SDLP in the Assembly election.
Ulster Unionist Assembly members, meanwhile, will have their first taste of the pressures to come when the Assembly meets for the first time on Wednesday. DUP and UKUP members are set to oppose the election of Mr Trimble and Mr John Hume as First and Deputy First Ministers-designate.
Under the Assembly's rules, the motion for election must carry the candidates for both posts, obliging Ulster Unionist and SDLP members to vote for both men simultaneously.
The UKUP leader, Mr Robert McCartney, last night signalled his intention to challenge Mr Trimble and Mr Hume to say whether they would sit in the Executive with Sinn Fein without prior IRA decommissioning. On the assumption that Mr Hume's reply at least will fail to satisfy, Mr McCartney will challenge UUP members as to whether they can vote for Mr Hume knowing that he does not consider decommissioning a precondition for Sinn Fein's entry to the Executive.
Ulster Unionist sources last night described the move as "very clever", but said they believed newly-elected Assembly members would not break with Mr Trimble at this stage.