The Taoiseach, Mr Ahern, will seek to repair recent damage to his relationship with the Ulster Unionists at a meeting with Mr David Trimble on the margins of this afternoon's Anglo-Irish summit in 10 Downing Street.
The summit meeting between Mr Ahern and the British Prime Minister, Mr Tony Blair, is expected to confirm that the former US senator, Mr George Mitchell, will head the "review" of the implementation of the Belfast Agreement triggered by last Thursday's failure to appoint the power-sharing Executive.
Senator Mitchell will join Mr Blair and Mr Ahern at their meeting and is then expected to proceed quickly into a first round of talks with the Northern Ireland parties to hear their views on how the review process should be conducted.
But sources last night suggested that Senator Mitchell's first priority would be to secure a "very clear understanding of what the two governments want him to do" and the timescale within which it is to be done.
The Taoiseach is hoping to learn that Senator Mitchell is prepared to commit himself to up to three weeks of talks with the Northern parties in September. He also hopes to hear that the senator will meet the parties once or twice before the end of this month.
The Sinn Fein president, Mr Gerry Adams, insisted yesterday that the Belfast Agreement review should be "focused" and time-limited. He said that he had asked the Taoiseach to ensure that the review process was as short as possible.
"The unionist stance has been to delay the process, and therefore a lengthy review suits the unionists' stalling and delaying tactics", Mr Adams said.
He added that the target of the review should be the thing which had necessitated it in the first place: the unionists' "refusal" to begin the transfer of power.
British sources were playing down expectations of today's summit, suggesting that it would be "exploratory . . . fairly low key . . . the beginning of another process". The sources felt that it was unlikely to be "definitive".
In some British and unionist circles there is a growing feeling that the emerging timetable will be complicated, and perhaps inevitably extended, by the expected publication in September of the Patten Report on the future of the RUC.
Mr Trimble's discussions with Mr Ahern are likely to focus on his weekend suggestion that unionist "procrastination" would lead to a republican expectation that the May 2000 deadline for decommissioning would have to be extended.
The Taoiseach's office yesterday insisted that he had been "misinterpreted" - a view British sources were happy to go along with last night, after a furious Mr Ken Maginnis had called for an Irish Government statement before any further meetings were held between the UUP and Dublin ministers.
Mr Trimble has now made it clear to senior colleagues that he will not resign as First Minister-designate, in response to Mr Seamus Mallon's dramatic resignation as Deputy First Minister-designate last Thursday. However, there is confusion and uncertainty in official circles as to whether the standing orders requiring the election of a replacement for Mr Mallon, and the re-election of Mr Trimble on a joint ticket within six weeks, applies in the present "shadow" period prior to actual devolution.
Dr Mo Mowlam, meanwhile, is fighting a rearguard action to keep her job as Northern Ireland Secretary amid continuing speculation that she might be replaced by Mr Peter Mandelson in a reshuffle expected later this week or early next.
--(Additional reporting by Frank McNally)