The escalating street violence in Belfast and the re-scheduling of the Nice referendum will be key issues when the Taoiseach Mr Ahern and British Prime Minister Mr Tony Blair meet on the margins of the British-Irish Council summit in Jersey today.
The latest allegations about sanctioned IRA involvement with the FARC guerrillas in Colombia will also be high on the agenda.
Mr Ahern will seek assurances from Mr Blair that the British government will accept that Irish endorsement of a second running of the Nice referendum will not compromise Irish military neutrality, according to Dublin sources.
The Taoiseach has already been engaging in similar recent lobbying in Sweden, Finland and Spain. He believes that unresolved questions over how Nice could affect Irish neutrality were critical in the first referendum being lost.
Confirmation from Mr Blair and other European Union countries that Nice would have no bearing on Irish neutrality could be a significant factor in paving the way for the passing of the next referendum in the Autumn, the sources added.
The two leaders are due to meet for 60 minutes at Jersey airport this morning ahead of the British-Irish summit. They will also discuss what action can be taken to help defuse tensions at the Belfast sectarian interfaces.
There is growing concern in Dublin and London that the widening disturbances could threaten the political process. The two leaders have already discussed the violence in two phone calls since the Taoiseach was re-elected. This is their first face-to-face encounter since the election, and they are anxious to try to restore the primacy of politics in Northern Ireland.
The Minister for Foreign Affairs Mr Cowen and the Northern Secretary Dr John Reid outside of the scope of the British-Irish Council meeting are also holding separate talks in Jersey this morning on the sectarian trouble and what the marching season holds in store for Northern Ireland.
The two governments are worried that the violence and the allegations against the IRA over Colombia and Castlereagh have the potential to jeopardise the peace process.
The British-Irish summit is also being attended by the First and Deputy First Ministers Mr David Trimble and Mr Mark Durkan, as well as senior politicians from the devolved administrations in Scotland and Wales, and representatives from Jersey, Guernsey and the Isle of Man.
Mr Trimble and Mr Durkan are likely to raise their anxieties about the worsening situation in Northern Ireland. Mr Trimble may also avail of his meeting with Mr Ahern and Mr Blair to raise the latest reports that the IRA was using Colombia as a testing ground for its bomb-making engineering department.
The British-Irish Council is the third element of the three-stranded Belfast Agreement, which some Ulster Unionists, and Mr Trimble in particular, have argued is not being accorded the same significance as the North-South dimension of the agreement.