Ireland may not have a mandated government until July, as party votes on the matter may hold up proceedings.
A decision by Fianna Fáil on entering government may take until the end of next month to finalise, it has emerged.
A vote on government formation would normally take place at a specially convened Ard Fheis, Instead, Fianna Fáil leader, Micheál Martin, will chair a virtual meeting to ballot on holding a postal vote instead.
Around 70 National Executive members are expected to approve an amendment to the party constitution giving the go-ahead for a postal vote involving more than 16,000 members throughout the country. An outside accountancy firm will be tasked to oversee counting.
A copy of the programme for government will be forwarded with a voting paper to each member.
A party source said: "There will be provision for a six-day turnround in getting the ballot papers out to the membership and returned, so if it takes a week or more to get a policy agreed by negotiators and parliamentary party, it will take another fortnight or so to get votes in from over 16,000 members."
A senior party source in Limerick said the vote of members could be tighter than a lot of people expect: "While listening to the media, you would take it as a 'given' that Fianna Fáil will enter government with Fine Gael, a lot will depend on the detail of any agreed policy. Dublin should not be counting their chickens."
Likewise, the Green Party's members could also cause a bump in the road, as unlike the other two parties, they need a two-thirds majority of their members — north and south — to back the deal, with a well-documented division in the party membership about entering government with Fianna Fáil and Fine Gael.
The talks this week have continued slowly, with consternation continuing on issues around agriculture, linked to the climate emergency. Initial reports that the deal for government could be finalised this week have since been downplayed by the parties, with sources now predicting next week at the earliest.
Green Party sources have found the discussions "frustrating" with little movement on major policy changes to reduce emissions. However, sources within Fine Gael insist their priority will be the wellbeing of farming communities.
"A lot of frustration" has been reported by a number of sources from the talks, amid pressure to conclude negotiations in order to move forward with government and pass new legislation under the Offences Against the State Act which is due to run out at the end of June.
Micheal Martin, said: “The next couple of days are going to be absolutely crucial because that June deadline is a real deadline and that facilitates more momentum over the next day or two to get this over the line. I think the outstanding issues can be dealt with, with a bit of common sense and with a will to get them resolved."
There are no government formation negotiations scheduled for today.
Meanwhile, the eight Independent TDs in the Regional Group say they "had constructive engagement" with the leaders of Fianna Fáil, Fine Gael and the Green Party today.
The leaders updated the group on the progress on government negotiations, and all agreed on challenges of "housing, agriculture and health", according to convener, Denis Naughten.
Ministerial positions have not been offered to the independent group unlike in previous governments.