The British government is likely to resist any DUP rejection of the latest London/Dublin proposals to enable the restoration of Northern Ireland's power-sharing administration.
This emerged last night ahead of tomorrow's key meeting between the Taoiseach, Mr Ahern, and the British Prime Minister, Mr Blair, in London, which official sources confirmed is intended to lead the present negotiations to "the point of decision".
The Irish Times understands that Mr Blair has not ruled out the possibility of convening the suspended Stormont Assembly and putting the proposals to a vote.
Failure to carry the proposals and in turn appoint a new power-sharing Executive within the statutory six-week period would suggest either the closure of the Assembly or fresh elections.
Another possibility is that a change to the rules for the election of the first and deputy first minister could remove the need for an election for the posts. It would allow them to be filled by the same d'Hondt process which applies for the nomination of other ministers in proportion to the strength of the qualifying parties. This could force the DUP to accept its share of ministerial portfolios or see them go to other parties.
However, it is generally accepted that any attempt to "blame game" the DUP would turn on Mr Blair's ability to show he was able to assure Dr Ian Paisley that the IRA had signed up to all "the particulars" of the proposals he gave the DUP leader last Wednesday.
The apparent determination of both premiers to stick to their timetable and prevent slippage was underlined yesterday as Downing Street declared this "an important week" for the peace process. Number 10 was officially still planning for success and refusing to discuss alternatives.
However, there was speculation that the meeting would be dominated by consideration of "Plan B" if the DUP confirmed it would not enter into government with Sinn Féin ahead of the British general election, which is expected next spring.
Although timings could still be changed, Mr Ahern is scheduled to see Mr Blair after the latter's meeting with Dr Paisley and ahead of a meeting between Mr Blair and the Ulster Unionist leader, Mr David Trimble.
Senior DUP sources stressed last night that the party's decision would not be governed by electoral considerations. "Our position remains that if the deal is good enough, we'll take it."
At the same time the sources acknowledged that the proximity to the election appeared to deny the DUP time to "test" an IRA commitment to stand down and end paramilitary and criminal activity.
Mark Hennessy adds: The SDLP's concerns about the deal offered to Sinn Féin and the DUP have "not abated", said the SDLP leader, Mr Mark Durkan, in Dublin yesterday.
After a meeting in Dublin with the Taoiseach, Mr Ahern, and officials, Mr Durkan said he had been "filled in on aspects of the package". However, he was still concerned by the DUP's refusal to accept the joint election of the First Minister and Deputy First Minister. Fearing a DUP veto, Mr Durkan said: "We made it clear that parties should not be in a position to vet or veto parties'appointments. Nationalists should be able to appoint ministers of their choosing to departments of their choosing. That's equality."