Negotiations between Fianna Fáil and the Green Party on forming a coalition government will resume early today, following some signs that progress had been made during last night's session.
However, the Green Party, which had warned on Wednesday that talks had to finish by last night, has now set a new deadline of lunchtime today if its national conference meeting is to be called on Sunday.
Leaving the talks, one of the Green negotiators, Dan Boyle, said: "The best hopes of everyone have not been realised. We are going to have to look at the situation as it is."
Different interpretations existed about which issues remain as stumbling blocks, although climate change, taxation, hospital co-location and a ban on corporate donations are included.
In particular, Fianna Fáil has resisted the Greens' demands that the new government should order a 3 per cent cut in Ireland's annual carbon dioxide emissions to cope with global warming.
Fianna Fáil also resisted pressure to abandon its plan to cut the top rate of income tax by 1 per cent to 40 per cent, though the Greens are supportive of cutting the standard rate by 2 per cent to 18 per cent.
Last night, some Fianna Fáil sources with knowledge of the talks indicated that the M3 motorway, planned for near the Hill of Tara, and the US military's future use of Shannon were also obstacles.
However Green Party sources, concerned that the party would be portrayed as having demanded unrealistic compromises, insisted that these issues, while important to them, were not "deal breakers".
Speaking briefly shortly before 9pm, Mr Boyle said: "Obviously, we are going to have to talk to our respective colleagues. Tomorrow morning is the furthest we can push this out in any conceivable sense.
"The fact that some progress has been made indicates that we still think that there is a potential to reach that agreement. We are all realistic that the difficulties that have been there since the start of negotiations still have to be resolved.
"There is some progress on all of the issues. The question is whether there has been enough," said the former Cork South Central TD, who is representing the Greens in the talks along with Dublin South East TD John Gormley and the party's general secretary, Dónall Geoghegan.
The two teams of negotiators met for the fifth day of talks, which have now lasted over 30 hours, at 11am yesterday in Government Buildings, following separate meetings with their own colleagues.
The atmosphere darkened throughout the day amid clear signs that few, if any, of the major differences between the parties had edged much closer to conclusion.
Last evening's session, which lasted from 5pm until 8.40pm, did make progress on some or all of these issues, sources close to the talks said privately last night.
Speaking as he entered Government Buildings for the morning session, Mr Gormley said: "There are some outstanding issues which are of great importance to the Green Party, and we do want some resolution today.
"I understand from the other side that they see the need to address these issues. We can't go on talking for days like this, it is simply not tolerable," he said.
Returning in the afternoon, following a meeting with senior colleagues who included the other Green TDs and representatives of their councillors throughout the country, Mr Gormley said: "These are very difficult negotiations, and there is no guarantee that we will reach agreement.
"We are going back to discuss these difficulties. We have taken direction from our party members. Our party members are uppermost on our minds at this stage, but, as I say, it is going to be very difficult to reach agreement," Mr Gormley told journalists.
The Fianna Fáil team is made up of Minister for Finance Brian Cowen, Minister for Social Affairs Séamus Brennan and Minister for Communications, Marine and Natural Resources Noel Dempsey.