The final Dáil vote on the abortion legislation will now take place at midnight.
The Government is allowing two extra hours of debate on the final stages of the Protection of Life During Pregnancy Bill.
Taoiseach Enda Kenny offered to sit even later than midnight, but said the Dáil needs to complete this legislation.
"There have been very few bills, probably over the last 40 years that have had such extensive discussion and consultation, and debate in the house," he said.
"I have no objection to extending the time again tonight, if that be necessary.
"I don't have any difficulty in dealing with it for that period … but I'm going to get rid of it this evening."
The Taoiseach also said the Bill is not about any one TD, and that those who vote against the legislation will move outside the Fine Gael family.
It is expected that Junior Minister Lucinda Creighton will vote against tonight's Bill and will lose the party whip in the process.
Minister Leo Varadkar says it's not clear yet how many other members of Fine Gael could join her.
"I honestly don't know. It's reported I the media there are, maybe, three waverers," he said.
"We may lose one, we may lose two, we may lose three.
"As I said before, this is an issue that a lot of people feel very strongly about. In this case, there are a number of members of my party who feel that their very strongly-held opinions on this are more important than the party pledge that they signed."
Varadkar earlier warned that Lucinda Creighton may face an "uphill battle" to rejoin the Fine Gael party if she loses the whip later today.
Meanwhile, Deputy Peter Matthews made an impassioned plea in the Dáil for a free vote.
"My younger colleagues in our party are under a shocking stress- I can see it visibly," he said.
"They're going to vote with the party because they've signed a pledge, against their conscience - they've said it.
"I think that is absolutely perverse."