Northern Ireland's First Minister, Mr David Trimble, expects the suspension of the power-sharing Executive by next Friday if, as is widely expected, Gen John de Chastelain fails to report that actual IRA decommissioning is under way.
And in the ensuing political fallout, the Ulster Unionist leader believes, Senator George Mitchell will support his version of the "understanding" reached between the Ulster Unionists and Sinn Fein at the conclusion of the Mitchell review last November.
This became clear last night as British and Irish officials made a last-ditch attempt to win some concession from republican leaders which might avert suspension of the administration.
However, officials held out little hope of a breakthrough in terms likely to be acceptable to Mr Trimble amid clear indications that the UUP leader would give his verdict more or less immediately after receiving Gen de Chastelain's report.
This is expected to come during this afternoon's scheduled Assembly debate on an Ulster Unionist motion, if not before.
The Northern Ireland Office played down speculation that the Northern Secretary, Mr Peter Mandelson, might make a statement in the House of Commons as early as today. However, in the event of a deemed "default" by the IRA, sources close to Mr Trimble said, he would defer his threatened resignation as First Minister by "just a matter of days" to enable the Secretary of State to effect the suspension.
The UUP calculation is that, however reluctantly, Mr Mandel son will be obliged to suspend the Executive, knowing that if Mr Trimble resigns he would not have the necessary unionist votes in the Assembly at some future point to secure his re-election.
The assumption in political circles also is that, if Mr Mandelson concludes that suspension is inevitable, he would want to be seen to act speedily and decisively.
While maintaining that the IRA could yet meet the deadline and begin decommissioning "within half an hour, if they wanted to" the mood within the Trimble camp was described as "resigned" to a statement by Mr Mandelson confirming the reintroduction of direct rule before the week is out.
Sources close to Mr Trimble say they are confident that Senator Mitchell, the former talks chairman, will support the UUP leader's interpretation of the understanding reached between the Ulster Unionists and Sinn Fein in the Mitchell review.
The Irish Times has been told: "He [Senator Mitchell] said if either party defaulted he would not hesitate to say who failed to deliver. He knew the timetable we were operating by for the beginning of decommissioning."
The sources claimed that Senator Mitchell "was not put out" by Mr Trimble's subsequent decision to reconvene the Ulster Unionist Council on February 12th for a final decision on whether he and his Ministers should remain in the Executive, since this was actually beyond the January 31st deadline the Ulster Unionists had stipulated for the beginning of IRA disarmament.