The Taoiseach, Mr Ahern, and the British Prime Minister, Mr Tony Blair, are expected to meet soon to discuss the growing threat to the political process in Northern Ireland.
The search for a suitable date for a prime ministerial summit has been given added urgency by Mr David Trimble's unprecedented criticism of the British government's handling of the peace process - and his implicit suggestion that the power-sharing Executive might have to be suspended for a second time.
Citing the absence of IRA decommissioning as a reason for the original suspension of the Executive and other institutions last February, Mr Trimble, writing in the Daily Telegraph yesterday, warned: "I proved then that there is a bottom line, and it hasn't gone away, you know."
One source in the Trimble camp told The Irish Times yesterday he understood suspension was "one of the options the [British] government is looking at", as Mr Trimble himself concluded that "constructive ambiguity" as an instrument for managing the peace process had "lost its utility". Clearly now convinced that his leadership of the Ulster Unionist Party is under serious challenge, the First Minister turned the heat on the British government, accusing London of "feeding republicanism's insatiable appetite", demanding "a moratorium" on RUC reforms pending IRA decommissioning, and apparently reinstating his party's earlier demand for the retention of the RUC's "royal" title.
Mr Ahern and Mr Blair were reportedly apprised of the gathering storm before Mr Trimble raised the stakes yesterday under the headline "Unionists didn't sign up to this agreement". Sources confirmed that the Taoiseach and Prime Minister resumed telephone contact shortly after the conclusion of the British Labour Party conference, and would have an opportunity to review developments in Northern Ireland on the margins of an EU summit at the end of next week.
However, with the disputed Police (Northern Ireland) Bill due to become law in barely one month's time, Irish officials recognise the need to schedule what looks to be an inevitable negotiation on policing and a range of other issues over the coming weeks. Mr Blair has an important engagement in Warsaw tomorrow. However, Irish sources last night said if the Prime Minister's diary permitted, a meeting later this week or early next should not be ruled out.
The ferocity of the First Minister's attack on the Blair government - he accused it of "cravenness" and "surrendering to terrorism" - took British ministers and officials by surprise yesterday. One Whitehall source said the tenor of Mr Trimble's article did not reflect the nature of his most recent discussions with them.
As Mr Trimble's deputy, Mr John Taylor, conceded that a majority of unionists now opposed the Belfast Agreement, London was seeking to establish precisely what Mr Trimble meant in calling for "a moratorium on Patten" pending IRA decommissioning and "a complete reopening of the (RUC) name issue". "Does he mean it?" wondered the Whitehall source, answering his own question with the observation: "He probably doesn't know himself. Obviously he's feeling his way but it does represent quite a mood swing."
There was some measure of immediate relief for the Northern Ireland Secretary, Mr Peter Mandelson, as he prepares for a concerted Conservative attack on the Police Bill in the House of Lords.
In his article, Mr Trimble declared: "Unless the government decides very shortly to stop allowing everything to be turned into a precondition for terrorist disbandment, as it did with prisoner releases, there will be no agreement. That means a moratorium on Patten until decommissioning has occurred and a complete reopening of the name issue."
Pressed to define "moratorium", the Trimble source accepted that the Police Bill would continue its passage through parliament. Asserting "it's about more than the Bill", the interpretation seemed to be that Mr Trimble expects plans for downsizing in police numbers, for example, to be delayed until decommissioning has started and the security threat visibly diminished. On the face of it this accords with the British government's own declared approach to demilitarisation.
However, another source later speculated that Mr Trimble could see the Bill onto the statute book but seek an order delaying implementation.
Even if the UUP leader does not intend an immediate or direct threat to the Police Bill, however, there will be apprehension in the Northern Ireland Office if he is seriously seeking to revive proposals for a double-barrelled "Police Service of Northern Ireland - the Royal Ulster Constabulary". The SDLP and Sinn Fein regard even the retention of the words Royal Ulster Constabulary in the so-called title deeds of the Bill as a fundamental breach of the letter and spirit of the Patten proposals. In the past week, too, one of Mr Trimble's most senior supporters privately endorsed Mr Seamus Mallon's reported view that it would be near-impossible for Northern Ireland's fledgling institutions of government to survive the trauma of a second suspension.
The past week, of course, has been a long one in the politics of the Ulster Unionist Party. Indications by senior parliamentary sources that a further challenge would be mounted at the Ulster Unionist Council, were followed at the weekend by the clearest indication yet that Mr Jeffrey Donaldson MP will seek the party leadership if a vacancy is forced.
Understandable then that British ministers and officials, like the media, should suspect Mr Trimble of "feeling his way" as he assesses the prospects for survival.
However, a source close to the First Minister last night insisted it was wrong to interpret his developing position as a response to internal party pressures alone.
The source told The Irish Times that Mr Trimble had warned Sinn Fein leaders before the summer that failure to advance on IRA decommissioning would guarantee an autumn crisis. While London is apparently expecting another IRA "confidence building measure" - possibly timed to coincide with the UUP conference this weekend - the source said this was not the issue: "There was a promise of regular re-inspections and direct engagement with De Chastelain."
And ominously perhaps for both governments, the source said of the UUP's ongoing warfare: "There are two separate questions here. There's what Jeffrey Donaldson and company might do. And what David Trimble might do."
Asked to explain, the source said the Ulster Unionist Assembly Party "took it over the edge" last February and could do so again by a number of means. While confirming possible suspension was the key message of yesterday's Daily Tele- graph article, the source said that Mr Trimble's own resignation was now among the options being actively considered.
Attending such calculations is the determination of some of his closest supporters that Mr Trimble's leadership of unionism can, and should, survive even the collapse of the Agreement.
Last week in Brighton a leading Sinn Fein politician suggested that collapse was now a very real possibility. The two national leaders who invested most to bring the Belfast Agreement about now need to urgently reinvest time, energy, imagination and skill if it is to be secured. Mr Ahern's meeting with Mr Blair will not come a moment too soon.
