Senior pro-agreement unionists are warning that Mr David Trimble's attempt to expel three Ulster Unionist MPs who resigned the party whip on Monday could cost him his leadership in the autumn.
Influential figures within the party, previously loyal to Mr Trimble, have told The Irish Times that they will not be supporting him when the issue comes up for a final decision by the party's Executive Committee, probably in September.
This development coincides with confirmation that a small group of pro-Agreement UUP Assembly members and constituency officers met in secret last weekend to consider the possibility of sponsoring a "unifying" candidate capable of replacing Mr Trimble and bringing the party's civil war to an end.
The Lagan Valley MP Mr Jeffrey Donaldson is said to be sceptical about fresh overtures made to him by the pro-Agreement camp over the past few days. However it seems clear that signs of increasing unease within Mr Trimble's Assembly power base and elsewhere were a major factor in persuading the Rev Martin Smyth MP and Mr David Burnside MP and the former party leader, Lord Molyneaux, to resist Mr Donaldson's resignation threat and to continue their fight within the party.
Against that, Trimble aides last night insisted that failure to move against the dissident MPs would have prompted the resignation of at least three party officers.
Mr Trimble will seek to initiate disciplinary proceedings against the three MPs - Mr Smyth, Mr Donaldson and Mr Burnside - at an emergency meeting of party officers in Belfast this morning.
However, while Mr Trimble seems certain to carry the vote to establish a disciplinary committee, the indications last night were that an unusually high number of absences meant he would probably do so with a minority of the 14-strong team.
Mr Smyth - who, as party president, would normally preside at a meeting of the officers - has indicated he will remain for business at Westminster. Also expected to be absent are Trimble allies Sir Reg Empey, who is in Scotland, Mr Jack Allen, who reportedly left for Barbados yesterday, Lord (Ken) Maginnis, who is on his way to Switzerland, and Mr Jim Nicholson MEP.
With Mr Donaldson and Ms Arlene Foster thought likely to have the support of Mr James Rodgers, the Trimble camp last night confirmed they were expecting to win the vote by a six to three margin.
It is understood Mr Trimble was prepared to threaten resignation if any of his key allies refused to back him in seeking the disciplinary action he considers "forced upon him".
However one senior figure last night told The Irish Times: "The choice facing the party is either to implode or resolve its difficulties. This personality clash between David and Jeffrey has become a point of principle for both of them. I don't think I was elected to expel half the parliamentary party and I don't think the leader realises the knife-edge he is on."