The proposed timetable for the devolution of policing and justice powers to the Northern Assembly has re-emerged as a potential deal-breaker at the Leeds Castle talks, which begin tomorrow.
This became clear last night as a senior Democratic Unionist Party source ruled out firm commitments to resolve the policing issue within the timeframe envisaged by the Sinn Féin president, Mr Gerry Adams, and the Ulster Unionist leader, Mr David Trimble, during their failed negotiation prior to last November's Assembly election.
Mr Trimble and Mr Adams are understood to have established the mid-way point in the five-year lifetime of the present Assembly as the target date for the transfer of policing and justice powers, subject to IRA "acts of completion" in parallel with the necessary legislative process in the Commons.
Beyond a general statement of intent that the issue must be resolved, however, the DUP source suggested the party would not commit to anything like a two or 2½-year timetable because "it would not be honest".
Asked to explain why, the source replied he did not think "the necessary confidence would be established within such a period" to enable policing powers to be assumed by a partnership government at Stormont.
That said, the source acknowledged that securing Sinn Féin's consent for the policing dispensation in the North was a requirement of the agenda agreed by the parties and the two governments at the Lancaster House talks in early July, and also by Mr Blair's famous "acts of completion" speech in Belfast almost two years ago.
Downing Street again refused to be drawn on the continuing behind-the-scenes preparations for the Leeds Castle talks, which the British Prime Minister, Mr Tony Blair, considers the most important since the negotiations leading to the Belfast Agreement in 1998.
Asked for an assessment of the prospects for agreement by Saturday, a Blair spokesman would only say: "We are making progress, but it is still impossible to say that we're going to get there."
Asked if Mr Blair was serious about his apparent threat to wind up the Assembly in the event of failure, he replied: "He is certainly serious about thinking through why, if that is the position we reach, we do not have an agreement, and the implications of that."
Sinn Féin and DUP sources were dismissive of Mr Blair's threat to find "an alternative way" forward if the Leeds talks fail, apparently agreed that neither party requires the Assembly to maintain its ascendancy within their nationalist and unionist constituencies.
And both are maintaining that sufficient progress can be made over the next three days to make it impossible for the two governments to walk away from the present negotiating framework.