The tactic of a post-dated letter of resignation has been used previously by the UUP leader in his continuing attempts to force IRA decommissioning.
In February last year, Mr David Trimble's threat to resign, along with his UUP executive colleagues, led to the suspension of devolved powers to the institutions for the two months prior to the Hillsborough deal.
Six weeks ago, in a surprise announcement to the Assembly, Mr Trimble declared he had lodged a post-dated resignation with the Assembly Presiding Officer to come into force on July 1st if the IRA fails to "initiate a process that will completely and verifiably put IRA arms beyond use".
The letter is accompanied by a note indicating it should be opened on July 1st but may be withdrawn by Mr Trimble prior to that. It is widely accepted that only significant movement by the IRA on arms or the suspension of the institutions by the British government will prevent the resignation.
The resignation threat is considered a high-risk move. The Irish Times understands he discussed resigning with his advisers last November, but believed it was a move he "couldn't come back from" and instead introduced the ban on Sinn Fein ministers attending North-South Council meetings.
Unlike the confusion surrounding Mr Seamus Mallon's resignation in July 1999, a new election for the joint positions of First and Deputy First Minister must be held within six weeks as stipulated in the Northern Ireland Act 1998, which came into force on devolution.
Due to an ambiguity in the Assembly's Standing Orders the legality of Mr Mallon's protest resignation at the delay in establishing the Executive was queried and he was reinstated after the passing of an Assembly motion.
Sources close to Mr Trimble yesterday played down speculation Sir Reg Empey would be nominated as an alternate First Minister for the six-week period, which would enable the administration to continue operating normally.
If no UUP alternate is offered, Mr Mallon can remain in office but will have no power of direction. Civil servants will exercise most functions of the joint office except functions conferred directly on both men, including the chairing of executive meetings.
The election of a new First and Deputy First Minister will require a majority of nationalists and a majority of unionists voting in favour. This means the 28 UUP members, including anti-agreement member Mr Peter Weir, and two PUP members must all vote in favour. If UUP defections occur, the redesignation of members of the Alliance party or Women's Coalition to "unionist" would be necessary - they are currently classified as "other" within the Assembly.
If there is a failure to re-elect both positions within six weeks, the Northern Secretary, Dr John Reid, must give notice of the holding of Assembly elections two months later, effectively meaning the North's electorate may be forced to return to the polls in October.
Mr Conor Murphy of Sinn Fein, chairman of the Assembly procedures committee, yesterday stressed another suspension of the institutions by the British government would send "a strong message to the nationalist community as to where their commitments lie".
The suspension of the institutions by the British government prior to July 1st would avoid Mr Trimble's resignation and the subsequent necessity for a reelection. Suspension after July 1st would be less useful as a reelection would be necessary within six weeks of restoration.
If no suspension occurs, negotiations could continue over the six-week period but informed sources suggest this would be "risky" as a deal may not be reached or any deal could fail to satisfy a majority of unionists.
The First and Deputy First Ministers would subsequently be in danger of failing to be reelected with Assembly elections then unavoidable unless Dr Reid suspended to save the UUP and SDLP from suffering losses mirroring their recent poor performances in the Westminster and local elections.
However, an SDLP source stressed Sinn Fein would be mindful that even if electoral advances delivered Mr Gerry Adams as Deputy First Minister it could be coupled with Mr Peter Robinson of the DUP as First Minister. "They know that would be a recipe for disaster."