London and Dublin might yet be forced to an earlier-than-expected decision about suspension of the Belfast Agreement by the resignation of all unionist ministers from the Northern Ireland Executive within days.
This emerged as a serious possibility last night as the British and Irish governments continued intensive behind-the-scenes efforts to secure a breakthrough on IRA decommissioning and so prevent Mr David Trimble's post-dated letter of resignation as First Minister from taking effect on Sunday.
The British Prime Minister, Mr Tony Blair, and the Taoiseach, Mr Ahern, are expected at Hillsborough tomorrow to lead negotiations with potentially profound consequences for the agreement.
Up to last night the operative assumption in both capitals has been that, in the event of Mr Trimble's resignation, the other three Ulster Unionist Ministers, Sir Reg Empey, Mr Michael McGimpsey and Mr Sam Foster, would remain in post, at least during the six-week period stipulated by the Stormont Assembly's rules for the election or re-election of the First and Deputy First Ministers.
British sources said failure to secure a positive "result" at the end of this week could still represent "work in progress", with negotiations then set to continue between the governments and the pro-agreement parties during July and early August.
In that relatively benign scenario, the two governments would have at least six weeks to resolve the decommissioning/ demilitarisation/policing deadlock before, if faced with a continuing impasse, having to decide between the suspension of the Assembly and other institutions of the Belfast Agreement and fresh Assembly elections, in which the DUP and Sinn Fein might be expected to continue their recent advances.
However, the stated readiness of the Democratic Unionist Party's two Ministers to quit the Executive has apparently increased the possibility of a complete unionist withdrawal from Executive office in the immediate aftermath of Mr Trimble's planned resignation, which is due to take effect at midnight on Saturday unless there is an actual start to IRA decommissioning.
In a surprise move on Monday, the DUP said Mr Gregory Campbell and Mr Maurice Morrow would resign as Regional Development and Social Development ministers, respectively, if Mr Trimble's three colleagues quit their posts.
Mr Campbell said he and his colleagues wished to "send the clearest possible signal that the current system does not command the support of the majority of unionists in Northern Ireland".
It is understood that the Ulster Unionist leadership has not come to a final view on what it would like to see happen should Mr Trimble's resignation proceed in the wake of an abortive negotiation over the next 48 or 72 hours.
Opinion inside the party may be divided, since even some dissident Ulster Unionists have been reluctant to see the immediate collapse of the Assembly and Executive on the eve of Drumcree and as the loyalist marching season nears its climax.
The threatened crisis in the peace process may feature during Prime Minister's Questions in the House of Commons this afternoon. While Mr Blair could travel to Northern Ireland later this evening, the expectation appears to be that he and Mr Ahern will not arrive in Belfast before tomorrow morning.