The two men held a successful meeting in London this week. Although Mr Ahern is leader of Fianna Fail, the least favourite southern party for Unionists,reports say they established a reasonable relationship. Sources close to both say they believe they can work together.
This apparently modest advance may be of great importance to the talks process which, despite 18 months of effort, has yet to produce any fresh element of agreement among the parties. They have also signally failed to bring about any new relationship between the Unionist party, which is Northern Ireland's largest political grouping, and Sinn Fein.
Among the most critical issues ahead are the Unionist desire to see the territorial claim to Northern Ireland removed from the Irish Republic's constitution, and Dublin's ambition to establish powerful new north-south crossborder institutions. Such issues would be much easier dealt with if Mr Ahern and Mr Trimble develop a working relationship.
Mr Trimble has already displayed a penchant for doing business via frequent meetings with Tony Blair rather than in the more structured talks process, which involves a chairmanship team headed by former US Senator George Mitchell, British and Irish ministers and eight Northern Ireland parties.
There is speculation that he may prefer to deal directly with the Taoiseach rather than through the Dublin ministers and officials who attend the Stormont talks. The fact that the talks themselves have so far failed to generate momentum is blamed by some of the other participants on the Unionist party, which is accused of aiming for as slow a pace as possible.
Mr Trimble is an infrequent attender at Stormont, and is said to leave his party to be represented by comparatively junior figures. This has led some smaller parties to complain that the Unionists, and possibly the Irish government, have in mind an attempt to make a deal centring on the Unionists, Dublin and the nationalist SDLP, to the virtual exclusion of other elements.
Although Sinn Fein is now in the talks following July's IRA ceasefire, Unionists remain determined to do no direct business with the republicans. Unionist representatives do not speak to Sinn Fein delegates in the sessions or the corridors.
A representative of another party said: "Most of us want to negotiate but the Unionists hate Sinn Fein, they really truly hate them. To them they are dirt, they are enemies." With no meeting of minds in this area, the possibility of a new understanding between Unionists and Dublin is widely welcomed.
Parties are now giving ideas on how the talks might proceed with smaller sessions and less formal dialogue to encourage participants to be more flexible. One participant said: "It's tough going, there's no doubt about it."
On one level Sinn Fein may welcome the Ahern-Trimble meeting as a possible precursor of the type of engagement which has not existed until now. On the other, republicans will be alert to any sign that the Unionists could succeed in driving a wedge between them and the other nationalist participants.
The question of the durability of the IRA ceasefire continues to be an important issue. Some, especially on the Unionist side, believe it could end at almost any moment, and favour stretching out the talks in the expectation that it will collapse.Reuse content