With just days to go before the UUP annual conference, one of the party's dissenting MPs, Mr Willie Thompson, has warned that the North's First Minister, Mr David Trimble, cannot sell the concept of an executive involving Sinn Fein in the absence of practical arms decommissioning.
More than seven potential defectors over the Belfast Agreement now existed in the ranks of the UUP's Assembly group, making Mr Trimble's position precarious, Mr Thompson told The Irish Times yesterday.
He was speaking before a visit to Dublin for a university debate tomorrow. Mr Thompson has agreed for the first time to share a public platform with a Sinn Fein member, Mr Caoimhghin O Caolain TD.
The two men are to take part in the debate at Trinity College. Invited by TCD's Historical Society to debate whether immediate decommissioning is necessary, Mr Thompson said he made his own decision and "Sinn Fein don't decide where I go and where I don't go".
He said that if the peace process, which Mr Thompson calls the "appeasement process", failed, Mr Trimble's leadership of the UUP would also topple. "If the process falls, he falls. We cannot start on a new note."
Mr Thompson said winning the Nobel Peace Prize had put even more pressure on the UUP leader. Politically, many people might take the view that granting this award would make it harder for opponents of the Belfast Agreement to challenge Mr Trimble on decommissioning.
"There would be an element of truth in this, but it is not enough to carry the day."
Mr Trimble could not face down his opponents because he did not have the power. The margin of victory in the passage of the Belfast Agreement was not sufficient to allow this.
"He went down the road that isolated him from me. From a policy point of view, we are at completely different ends of the spectrum. But he is still leader of the party, and from that point of view we must treat him with respect."
He said Mr Trimble was unlikely to face any serious challenges at the conference because the event would be stage-managed.
There was now a great danger that the Belfast Agreement would come apart over decommissioning. Mr Trimble would be unable to promote any notion of Sinn Fein's involvement in the proposed executive without some kind of practical decommissioning.
He had no idea what the Sinn Fein MP, Mr Martin McGuinness, was discussing with the chairman of the independent commission on decommissioning, Gen John de Chastelain. The general was there to oversee the mechanics of decommissioning, and he [Mr Thompson] did not believe he had a role in when it actually happened.
He said the entire basis of the agreement was unsound. The idea of making decisions while attempting to please all the Assembly parties was "a recipe for doing nothing . . . it is not workable".
If the agreement did fall, the British and Irish governments would not be able to implement it over the heads of unionists. The only way to govern Northern Ireland was by direct rule from Britain with the restoration of local government powers.
Mr Thompson and Mr O Caolain have been invited by the College Historical Society to debate decommissioning, along with Prof Ruth Dudley Edwards, the former British Labour party spokesman on Northern Ireland, Mr Kevin McNamara, and a Queen's University historian, Prof Arthur Aughey.