The fate of Northern Ireland's power-sharing Executive seems set to be sealed at today's Downing Street meeting between Mr Tony Blair and Mr David Trimble.
With the DUP's two Ministers ready to withdraw this morning, the Ulster Unionist leader is expected to press the British Prime Minister to table a motion for debate in the Stormont Assembly proposing Sinn Féin's expulsion from the Executive.
If the SDLP will not back Sinn Féin's exclusion, Mr Trimble would expect the British Government to proceed to suspend the institutions of government established under the Belfast Agreement.
Mr Trimble is likely to leave Mr Blair in no doubt that the Ulster Unionists will otherwise force his hand by withdrawing their Ministers from the power-sharing administration. Authoritative sources have told The Irish Times that Mr Trimble expects to leave Number 10 this afternoon with "clarity" about Mr Blair's intentions.
Mr Trimble is operating to a much shorter timescale that that originally envisaged by the Secretary of State, Dr John Reid, who hoped to have almost two weeks in which to rescue the crisis in the political process, sparked by an alleged republican spying operation at the heart of the Northern Ireland Office.
Last night, the PSNI said a third person had been charged on two counts of having documents likely to be of use to terrorists. He is due to appear at Belfast Magistrates Court this morning. A fourth person remains in custody.
DUP Ministers Mr Peter Robinson and Mr Nigel Dodds initially said they would resign their posts if Mr Trimble pulled out of the Executive with his Ministers and they notified the Assembly speaker to that effect.
But the DUP yesterday evening toughened its position and decided to take a pre-emptive strike by saying it will withdraw from government today, thus increasing pressure on pro-agreement elements.
Technically the DUP has seven days to re-nominate or else the posts will be offered to other parties. Ulster Unionists, however, described the move as a stunt and insisted that the political initiative rested with Mr Trimble at his meeting with Mr Blair.
The First Minister indicated yesterday that the Executive and other institutions of the Belfast Agreement do not even have a lifeline of a week. "I must say, without dramatic developments, I have great difficulty in seeing how the Executive as presently constituted can meet again," he told members during Question Time.
A series of crisis talks in London, Dublin and Belfast are planned for today and the rest of the week. Mr Blair and the Taoiseach, Mr Ahern, will hold what could be a difficult summit meeting in Downing Street tomorrow night.
Both governments are increasingly fatalistic about the prospects of maintaining the institutions but differ in their preferred methods of cushioning the damage to the agreement. London fears that the only way to limit the political fallout is to suspend the institutions indefinitely in the hope that in the medium- or longer-term they can be re-established.
In the absence of a rescue package that would see the Executive continuing to operate, Dublin favours fresh elections followed by negotiations - a move Mr Blair is likely to resist.
In Dublin last night, speaking after a meeting with Mr Ahern, Mr Gerry Adams said the DUP Ministers would have to come back. The Sinn Féin president said one of the concerns Mr Trimble expressed when he last met him was that the DUP was going to "leapfrog" over the UUP. "He had some wind that the DUP were going to bring in letters but he was talking then about the early spring of next year," he said.
"The DUP have a vote. The people who vote for them have rights, they will want to see their position represented and the DUP will have to come back."
Mr Adams said all of those who supported the Belfast Agreement had to ensure that the damage done by the departure of unionists was minimised by everybody else "and particularly by the two governments".
He said: "If there is a crisis, in any crisis, whether it's a contrived crisis or a real crisis, then it goes over to the people to decide what the outcome should be, and there shouldn't be any sort of a structure which has some sort of super referee from London coming in to take away from the natives whatever little political structure that they have bestowed on us.
"If I was a unionist, I would have grave concerns but it is still my view that there is a solid block of unionists there that want this process to work."