Failure tomorrow to break the political deadlock could result in an Assembly election that the three pro-Belfast Agreement parties don't want, according to a senior talks source.
The Northern Secretary, Dr John Reid, has already suggested that if the talks fail, an autumn election could follow, while yesterday one senior Irish insider agreed such an election may be inevitable in the event of a continuing impasse.
The SDLP and Ulster Unionists could face further electoral damage in such a poll and while Sinn Fein could gain extra seats, senior party sources insist they do not want an election.
The Irish source said Friday was being viewed by the two governments as an absolute deadline. If the stalemate continued, then elections, rather than suspension of the Assembly and Executive, may have to follow, he added.
The talks are adjourned today to allow unionist negotiators attend the Twelfth celebrations. Before leaving Weston Park yesterday evening both Mr Ahern and Mr Blair reaffirmed their conviction that the Belfast Agreement was the only way forward.
"The Good Friday agreement has worked well most of the time," said Mr Ahern. "It has given a lot of security. It has given a lot of help and assistance to a lot of opportunities to the development of a new economy and tourism, all of the institutions, the work of the institutions."
Mr Blair said there were still "substantial areas of disagreement and difficulty" but he remained hopeful that a resolution could be achieved.
Unionists complained yesterday that little progress had been made. The SDLP and Sinn Fein, after concluding their negotiations around tea-time yesterday, agreed that some progress was made on policing and demilitarisation, although, particularly in relation to policing, not enough to satisfy nationalists.
However, the former Deputy First Minister, Mr Seamus Mallon, accused republicans of failing to make any moves on IRA weapons. "There have been some advances but on one of the central issues, and I will be specific, about dealing with illegally held arms, there isn't the clarity yet that is required."
Mr Adams said that if there was no progress on certain issues Mr Mallon must also bear responsibility. "He cannot hang the issue of weapons around Sinn Fein. It is his responsibility as well as everyone else's," he said.