The leaders of Fianna Fail, Fine Gael and the Green Party have had a “constructive meeting” as part of the latest talks aimed at forming a coalition government.
The meeting at Agriculture House in Dublin ended on Sunday evening.
A Fianna Fail spokesperson said Micheal Martin, Leo Varadkar and Eamon Ryan had “made progress with many outstanding issues”.
“All parties will continue the talks tomorrow,” they added.
The pension age, policy over carbon emissions, agriculture and housing are believed to be among the final sticking points.
The three parties are also speaking to groups of independent TDs to try to secure their support, some 120 days since February’s inconclusive general election.
There has been speculation that a deal could be announced on Thursday.
Fine Gael’s Martin Heydon described the process to date as “lengthy”.
“The negotiating team and staff have worked morning, noon and night over the last number of weeks,” he told RTE, adding “good progress” had been made.
“But there is still some really significant outstanding areas as well.
“I would be hopeful that we could get an agreement before next weekend but it’s by no means guaranteed.”
Fianna Fail’s Marc MacSharry said “what is important now is that the negotiations come to a conclusion”.
He added: “It has involved compromise so far, there are still some difficult issues outstanding but we’re very hopeful they can be dealt with.
“We’re all hopeful, it’s in everyone’s interests including the nation as a whole, that we have a programme for government that’s capable of facing the enormous challenges that we face.”
Sinn Fein TD David Cullinane has criticised the potential coalition government as “not representing the type of change people voted for”.
“I think there is zero chance of parties who have been in power since the foundation of the state bringing about the real and transformative change that we need to see happen,” he said.
Meanwhile, Mr Ryan is set to face a challenge after his deputy declared she will run against him in a leadership race.
However, Catherine Martin said she will not run against the Greens chief until after the government formation talks process has concluded.