The Ulster Unionist Council is to discuss a motion calling for outright rejection of the two governments' Joint Declaration, and reaffirming a position adopted by the council last September.
That council meeting demanded that no Ulster Unionist would "sit in government with unreconstructed terrorists" and called for, among other things, "the total disarmament and disbandment of all terrorist groups including the IRA".
The Irish Times understands the motion to go before the 900-member council on Monday, June 16th, will read: "The Ulster Unionist Council reaffirms the unanimous resolution of 21st September 2002 and rejects other proposals linked to the Joint Declaration published by the British and Irish governments."
Mr Jeffrey Donaldson has resisted pressure not to go ahead with the UUC meeting on the basis that retention of the Royal Irish Regiment (RIR), the issue which helped spark the current controversy within the UUP, is to be discussed by the party's executive meeting tomorrow.
Amid signals that the British government is to announce some form of reprieve for the home battalions of the RIR, The Irish Times was told that there has yet to be agreement on what any statement expected next week could contain.
A well-placed British source suggested that unionists were "getting all steamed up" over an issue that would not arise for some four years
However, despite this, opposing sides within the UUP stepped up public criticism of each other.
Mr Fred Cobain, a senior UUP figure, said more time should be allowed for discussion of the Joint Declaration produced by the British and Irish governments in April.
He also claimed that there was a need for cooler heads to prevail within the UUP.
Denying that divisions were over policy, he added: "Seven or eight individuals from both sides are determined to get their way. We need to get away from that."
Other Trimble loyalists rallied yesterday, claiming that Mr Donaldson had misread the broad opinion among UUP members. One source told The Irish Times: "Jeffrey has not played this at all well."
Referring to comments among grass-roots members, the source added: "They're asking, 'what the hell's he at'?"
It was also suggested that Mr Donaldson was behaving "like a spoilt brat in the schoolyard".
In an article in last night's Belfast Telegraph, one of Mr David Trimble's advisers said that the threat of resignations over the Joint Declaration were ridiculous.
Referring to the Donaldson wing, he wrote: "Presumably, their intention is to set up yet another unionist party - just to make sure Sinn Féin is the largest elections party next time. It would be absurd if it were not so serious."
He likened the actions of those calling for the UUC meeting on June 16th as more akin to masochism than unionism.
In a letter to the same newspaper, a former Stormont minister denounced Mr Donaldson's tactics against the leadership as "sheer lunacy".
"We do not shoot ourselves in the foot any more. We shoot ourselves in the head to destroy for good and all," he said.
A former UUP member who joined the DUP said the current dispute within the UUP did not arise from plans to stand down the home elements of the RIR.
Mr Peter Weir said disagreements were founded in the UUP's commitment to the Belfast Agreement, which he described as a "fatal flaw".
"It is only be following the DUP policy of seeking an entirely new agreement can unionists halt the decline. David Trimble had already sacrificed the RUC and the RIR. If left unchecked what will he give away to complete his hat trick?"
Sinn Féin, which has demanded the abolition of the RIR's home battalions, yesterday called for implementation of the equality elements of the Joint Declaration.
Former minister Ms Bairbre de Brun demanded movement on a range of equality indicators, and said: "I have sought a meeting with Des Browne [a Northern Ireland Office minister] at the earliest opportunity to clarify how the British government will implement their commitments in the rights and equality field."
The Joint Declaration held out the promise of progress, she added. "People now need reassurance that this will become a reality."