Social Democrats co-leader Róisín Shortall has warned that a Government may not be formed until Easter.
The party met with Sinn Féin to discuss policy, which Ms Shortall said was a “good engagement across four different policy areas”.
However, she warned that government formation was still some way off.
“The likelihood is that we’re talking about sometime around Easter. I mean, it is early days yet and when you look at the previous times it has taken to form a government, the last time was 74 days.
“But we are at early days – Fianna Fáil and Fine Gael haven’t had policy discussions as of yet. Equally, there is potential for other combinations in relation to the other parties.
“We are engaging very actively with other parties.”
Ms Shortall accepted that there is not the requisite number of TDs to form a left-leaning government and said that it was incumbent upon the larger parties to come to an agreement.
“It will require two of the medium-sized parties to come together in some arrangement.”
Her co-leader Catherine Murphy said that forecasting the length of time it will take to form a government was “crystal ball territory”.
“All we can do is control what we can control and that’s our engagement with other parties.”
Both co-leaders said that the public accepts that the Dáil arithmetic means that government formation will take some time. They said there was not yet any sign that the public was angered at the pace of talks.
“People are asking ‘how do you think it will pan out’,” said Ms Murphy.
“But overall, people are prepared, if it’s the right arrangement, to accept that there is an investment of time needed.”
Ms Shortall reiterated that the party is unlikely to change its position that it will not join a Fianna Fáil-Fine Gael coalition government.
“People made a very clear statement on February 8 – they want to see a change and a change of direction. It’s impossible to see how that can happen if you have more of the same with Fianna Fáil and Fine Gael.
“You can only judge Fianna Fáil and Fine Gael working together on their record over the last four years and that record has failed in a number of key areas.”
The Social Democrats will hold a full-day negotiating session with the Green Party tomorrow, before meeting Sinn Féin again on Thursday.
Meanwhile, Sinn Féin TD Pearse Doherty called the meeting "constructive".
“Today we had a very constructive meeting with the Social Democrats in which we discussed common progressive policies and manifesto commitments and we have agreed to meet again on Thursday," said Mr Dohery who added that the two parties had "found many areas of common ground".
Sinn Féin will meet People Before Profit, Independents4Change, the Regional Independents this week and the Green Party on Friday.