At his party's annual conference two weeks ago, Mr David Trimble spoke of applying a "considered and calibrated approach" if the IRA failed to move on its pledge to put its arms beyond use.
On Saturday Mr Trimble may have to spell out in dangerous detail to his 860-member Ulster Unionist Council what he means by this phrase if he is to continue as party leader and, more problematically, if the Belfast Agreement is to keep motoring.
The current talk is that he means a phased withdrawal from working the institutions of the agreement, including the Executive. In other words, he is partly moving on to the territory occupied by the No camp. Yet he is attempting to do this "in a sophisticated and subtle fashion", as one of the Yes unionists said yesterday.
"He is treading a fine line. He doesn't want to collapse unionist support for the agreement but he also wants to ensure that his own support in the party doesn't collapse," the Yes source said.
At the moment anti-agreement unionists are not in a mood to be impressed by sophistication. "Read my lips: no guns, no government," is their message. Since the Belfast Agreement was signed 30 months ago, Mr Trimble is reckoned to have survived 21 explicit or implicit attempts to oust him as UUP leader: the old death-by-a-thousand-cuts routine.
By various strategies and ruses, he has outflanked or side-stepped his tormentors. He is again trying to finesse the No camp by moving towards it.
It's a dangerous strategy and his fiercest opponents within the UUP believe it is ultimately doomed to failure. Yet others in the No camp at least are prepared to listen.
Mr Jeffrey Donaldson yesterday attempted to dampen down reports that Mr Trimble is seeking to find common ground with him. However, he confirmed to the Belfast Telegraph that the two wings of the party were in contact at a "low level".
Mr Trimble is exploring whether a strategy of a step-by-step disengagement from the agreement, eventually resulting in withdrawal from the Executive, could serve to unite the party - or at least swing some No or wavering Ulster Unionists behind him.
At the same time he is trying to achieve this in a "flexible" manner which somehow avoids deadlines. No ultimatums or deadlines was Mr Gerry Adams's warning yesterday. At the time of writing it looks like an impossible dilemma.
As Mr Trimble indicated at his annual conference, his tougher stance could first involve withdrawal from the North-South element of the agreement, followed by other phased measures and culminating in a walkout by UUP ministers from their departments.
This, logically, would lead to the suspension of the Executive or the collapse of many elements of the agreement.
As one seasoned London observer put it yesterday, Mr Trimble has nothing else to sell to his council. "He's got to have a script," he said.
Pro-agreement unionists hoped that this week Mr Trimble could point to a new substantial IRA confidence-building measure on arms, and some concessions on Patten.
The Police Bill, currently moving towards completion in Westminster, appears to be moving towards an "unsatisfactory draw", with both unionists and nationalists angered by the way Mr Peter Mandelson is fashioning its final shape.
On arms, there is no sign of a second IRA weapons inspection or of any greater engagement with Gen John de Chastelain's decommissioning body.
So, as the London source would have it, Mr Trimble can plausibly argue there is no alternative to the agreement. Yet he is short in his ability to tell the unionist council of his great achievements on arms and policing.
His room for manoeuvre is becoming limited. Or to quote one of his senior pragmatic allies, "the rein is tightening."
Implicit in all this is that the advantage is with the No side. There is speculation that Mr Trimble is now reluctantly prepared to impose a decommissioning deadline of March but that, at the very least, Mr Donaldson is holding out for a deadline of Christmas set in stone.
All of the foregoing must carry the political health warning that a week is a long time in politics. Much can happen between now and Saturday. If the IRA moved quickly and significantly on weapons, Mr Trimble's position would strengthen - although the No unionists would dismiss such a move as a republican stunt to save the First Minister.
The bottom line, though, is that at the moment Mr Trimble doesn't have a script.