British Prime Minister Mr Tony Blair's decision on an Assembly election for November 13th is now believed to be imminent.
Speculation about Mr Blair's intentions built dramatically last night ahead of discussions later today between Mr Gerry Adams and Mr David Trimble in Belfast.
Mr Blair is expected to sign off on his decision after early talks in London with the Taoiseach, Mr Ahern.
Informed sources said last night the two leaders could yet allow more time for the ongoing negotiations between the Sinn Féin president and the Ulster Unionist leader.
However, following Mr Blair's latest Downing Street talks yesterday with Mr Adams and Mr Martin McGuinness, the growing belief in Whitehall is that it is now a question of "when, rather than whether" an election - with Mr Blair and Mr Ahern likely to bow to the opposition of the Northern Ireland parties to a December poll.
Mr Adams and Mr Trimble are due to meet again later today in an atmosphere of mounting excitement fuelled further by the news that the Independent Monitoring Commission (IMC) is to hold its first meeting in shadow-form in Belfast tomorrow.
Whitehall sources insisted, however, that this preliminary meeting of the IMC was not part of any "choreography" presaging a deal on IRA and British Government "acts of completion" enabling an Ulster Unionist commitment to resume power-sharing with Sinn Féin following an election.
And it remained unclear last night whether Mr Trimble would again oppose calling an election in the absence of a prior agreement with Mr Adams.
Citing massive Irish and American pressure on Downing Street, a senior Sinn Féin source told The Irish Times: "We think Tony Blair realises he made a mistake in cancelling the election earlier this year and that ... the argument is won."
However he said this prediction came with "a health warning" that Mr Trimble "by dint of his personality and the strength of any wobbly he throws, might change his (Mr Blair's) mind".
One British assessment last night suggested Mr Trimble "appreciates it's going to happen and isn't actually against it".
However Sinn Féin's caution seemed to be borne-out by the continued insistence of the Trimble camp that "the prime minister needs to have good reason to reverse his position of last April".
One UUP insider said last night: "I think Tony Blair is very cautious, very focused on the need to ensure the stability of the institutions. If there is no agreement (with Sinn Féin) that leaves us with very serious problems."
Mr Trimble and Mr Adams are expected to exchange further draft texts covering key aspects of their ongoing negotiation, including the demand for an end to IRA paramilitarism as defined in the British/Irish Joint Declaration; the sustainability of the institutions of government; and the timetable for the transfer of policing and justice powers to the Stormont Assembly.
But while London professes hope that the continuing UUP/Sinn Féin dialogue signals the potential still for a deal, each side last night offered conflicting assessments of the prospects for resolving all the outstanding issues ahead of a decision by Mr Blair on whether to call the election.
Despite their assertion that republicans remain "a long way short" of agreeing the terms prescribed by the Joint Declaration, the UUP appeared optimistic that significant movement would take place over the next few days.
One source close to Mr Trimble said his "hunch" was that it was "more likely than not" that agreement would be reached and that the election would go ahead.
Against that, while allowing that agreement was possible, the Sinn Féin source said: "At this time the election is most likely going to be fought in the absence of a deal."