Mr Tony Blair could be forced to scrap the existing talks process if the Ulster Unionists carry out their threat to block his timetable for the start of all-party negotiations on the future of Northern Ireland. In spite of the hopes raised by the weekend confirmation of a renewed IRA ceasefire it has been learned that at their lunchtime meeting at Downing Street today Mr David Trimble will tell the British Prime Minister that his party will not enter negotiations with Sinn Fein on the terms agreed by the British and Irish governments.
Barring significant last-minute concessions - which Mr Trimble privately concedes to be unlikely - senior Ulster Unionists say they will use their veto at Wednesday's crucial session of the Stormont talks to block the London Dublin formula for dealing with the decommissioning issue alongside the political negotiations. And the sources, close to Mr Trimble, said the effect of that could be to oblige Mr Blair to "scrap the present talks structure and convene a different form of conference".
The Irish Times has previously reported that Mr Blair would be prepared to do precisely that if he became convinced that the process, in its present format, was unlikely to facilitate his plan to have a settlement in place by next May.
However, with September 15th the effective deadline, the British and Irish governments will resist any precipitate moves to seek an alternative talks structure.
Mr Trimble is expected to stress to Mr Blair, and at a subsequent Westminster press conference, that "he is not walking out (of the talks) at this stage." And he is likely to risk internal party criticism by insisting that "he is not saying `never"' to the possibility of sitting down at the talks table with Sinn Fein.
However, while the British government might seize on that to buttress hopes of keeping the UUP aboard the so-called "settlement train", the Irish Government, the SDLP and Sinn Fein would expect Mr Blair to face down the threatened disruption of the agreed timetable for negotiations which was such a vital factor in securing the restoration of the IRA ceasefire.
The prime minister will today confirm again his intention to have the proposed Independent Commission, tasked to address the decommissioning issue, in place before the scheduled negotiations in September. But it would seem impossible for Mr Blair to meet Mr Trimble's demand for an explicit amendment to the British Irish proposals, confirming an objective to secure decommissioning "in parallel" to the negotiations.
Despite this hardening of their demands, Dr Mo Mowlam, the Northern Ireland Secretary, yesterday refused to accept "that the unionists are yet lost". But Mr John Hume, SDLP leader, said the talks should proceed "if any party walks out" because the commitment was to put any proposed settlement to the people for their approval in a referendum.
Senior Dublin sources, too, maintain the talks could proceed despite any unionist withdrawal. However, the unionist parties say this option does not exist. Mr Peter Robinson, deputy leader of the DUP, maintained: "You can't have talks if unionists aren't there. There is no way any unionist is going to accept this. Without unionists you can't have talks, and under the rule that is the end of the process."
The "rule" Mr Robinson referred to requires what is termed as "sufficient consensus" - the support of a majority of the unionist and nationalist delegations - to agree any item on the agenda. If that is not forthcoming on Wednesday it would amount to an outright rejection of Dr Mowlam's demand that the business of the opening plenary be cleared to permit the start of the substantive negotiations on September 15th.