Intensive negotiations on a programme for government resumed yesterday between Fianna Fáil and the Green Party after contacts between the sides were re-established over the weekend.
Yesterday's exchanges took place after Fianna Fáil negotiators worked late into Sunday night on a response to a Green Party document received earlier in the day.
That document outlined what the Greens saw as the main unresolved issues between the parties.
Yesterday morning the Fianna Fáil negotiating team, including Ministers Séamus Brennan and Brian Cowen and advisers, resumed their consideration of the Green Party document in Government Buildings.
Meanwhile, a Green Party negotiating team of party chairman John Gormley, Dan Boyle and party general secretary Dónall Geoghegan met at party headquarters in Suffolk Street.
Late morning, Fianna Fáil sent a message to the group to say that its response was ready and John Gormley walked to Government buildings to pick it up at about 12.30pm.
Meanwhile, the Taoiseach and Trevor Sargent had what was described as a "courtesy call" and agreed to be on standby to meet later in the day if progress was made.
Mr Ahern spent several hours in Government Buildings and left at around 5pm.
Outside the Green Party head office at lunchtime, Trevor Sargent had said the difficulties, which caused the collapse of talks on Friday, remained but he hoped they could be "ironed out".
He said Fianna Fáil's response to the Green Party document was being examined and the difficulties might not be as "insurmountable" as Fianna Fáil had thought.
Mr Sargent said calling a party convention to approve any agreement before the Dáil meets on Thursday would be a "logistical nightmare", but if they had to do it they would, although he stressed that time was running out.
At about 5pm Brian Cowen left Government Buildings saying he believed a fair offer had been made in talks with the Green Party on the possible formation of a new government.
At the same time on RTÉ radio Dan Boyle said progress had been made on a number of issues, but that a number of problems remained. He hoped that within the hour it would be clear if progress had been made.
At 7pm Mr Ahern returned from his office, St Luke's in Drumcondra, to Government Buildings and Mr Sargent was seen in Leinster House. They were unable to conclude a deal last night, but the talks will continue today.