Uncertainty about London's absolute commitment to fresh Assembly elections in May could still prove a major factor in continuing attempts to forge a British/IRA deal on "acts of completion".
This has become clear at the start of another week of intensive negotiations ahead of next Monday's "deadline" which will see the British Prime Minister, Mr Blair, and the Taoiseach, Mr Ahern, back in Belfast for make-or-break talks with the pro-agreement parties.
Mr Ahern and Mr Blair will prepare for that summit during a scheduled one-hour meeting in London on Thursday, at which they will review progress made thus far and determine what remains to be done in the time they have assigned.
The very involvement of the two prime ministers is fuelling speculation about a likely breakthrough sufficient to win an Ulster Unionist commitment to resume power-sharing with Sinn Féin after, if not before, elections in May. At the same time, British sources maintain the critical missing element in the current negotiations "is a clear indication of what the republicans are prepared to offer" to secure such an outcome.
Sinn Féin sources in turn say they are "nowhere near" a deal on further policing reform and remain highly suspicious of British proposals for radical moves towards "normalisation" in Northern Ireland over a three-year period - citing similar promises they say were made during the Weston Park negotiations in July 2001 and subsequently broken.
Seasoned observers note that an elaborate game of bluff and counter-bluff could still prove the precursor to a successful conclusion to the present negotiation, which "will almost certainly go right down to the wire, if not beyond it".
However, last Friday's talks in Dublin revealed some shared concern among Irish and British ministers and officials about a perceived "lack of urgency" on the part of republican negotiators. And there is evident anxiety in London that the IRA may have determined to play its game long, with a definitive negotiation on "acts of completion" to await the outcome of the UUP's electoral contest with Dr Paisley's DUP. London's uncertainty is rooted in continuing suggestions that Sinn Féin's approach to any possible deal is not in fact predicated on Mr David Trimble's acceptance of it as the basis for restoring devolution.
Until now, Downing Street has dismissed all speculation about the election date, insisting Mr Blair's purpose is to secure a comprehensive deal enabling the Ulster Unionists to recommit to power-sharing and so rendering questions about May 1st irrelevant.
However, usually reliable Sinn Féin sources have again told The Irish Times they think "there will be no deal with Trimble", and that fresh elections could be followed by a repeat of the experience of the first Assembly, which took 18 months to secure the appointment of a power-sharing Executive.
Confirming that "we could be in for the same sort of brinkmanship again", the sources said they accepted that holding the election offered no guarantee of an early return to devolved government.
At the same time they expressed confidence that that would be the eventual result of "a realignment within the DUP" and within unionism generally.
London will be hoping this is "bluff" ahead of a significant move by the IRA toward its complete cessation as an active paramilitary organisation. Yet if Sinn Féin really does think to move ahead "with or without Mr Trimble", this could hugely complicate Mr Blair's final judgment call on whether or not to proceed to elections.
The present Sinn Féin expectation appears to be that the elections will go ahead as scheduled, even if the current negotiation proves "inconclusive" in terms of IRA "acts of completion" and reciprocal British commitments on the full and final implementation of the Belfast Agreement.
However, it seems clear that London has not yet ruled out the possibility of introducing legislation giving it the power to postpone the elections for either a fixed or indeterminate period.
In Dublin on Friday the Northern Ireland Secretary, Mr Paul Murphy, repeated the familiar formula that he had "no plans" to change the election date. However, it is privately acknowledged that this does not translate into a hard and fast commitment to hold the election on the due date.
While insisting that British ministers and officials remain determined on success and have not even addressed the issue, one informed source last night conceded: "If the outcome is a pale shadow of what the Prime Minister has demanded, then he could come under strong pressure to postpone."
While London probably shares Dublin and Washington's view that Mr Trimble cannot be the final arbiter on any deal, Mr Blair might find it difficult to face down the UUP leader over an election consequent on an IRA offer he himself considered short of what is required.