The reopening of schools next month has been thrown into doubt after the Tánaiste said that he couldn't guarantee pupils would be back in classrooms.
Leo Varadkar said that while case numbers are dropping, they are still quite high.
His remarks in the Dáil came only hours after Taoiseach Micheál Martin said that the reopening of schools will be on a phased basis and likely start from March 1.
Mr Martin said the "indications" are that it will likely be at the beginning of March during a radio interview on Thursday morning.
But Mr Varadkar said the date has not yet been formally approved by public health officials.
"If we have learned anything from the pandemic in the past year, it is that nobody can give a guarantee or offer absolute certainty," Mr Varadkar added.
"We are seeing case numbers coming down but they are still quite high.
"There are still 500, 600 or 700 per day.
"We just cannot say for sure what impact it will have as schools reopen on a phased basis throughout March and April."
The Cabinet sub-committee on Covid-19 is meeting today to discuss proposals of bringing Leaving Certificate students and junior and senior infants back into the classroom next month.
First and second class pupils may also return to school in the coming weeks, according to Mr Martin.
The Taoiseach's comments have been criticised by opposition parties.
Labour leader Alan Kelly said there is genuine concern among teachers, parents and students.
"Why kite-fly (the) first of March? Why not have the meeting of the sub-committee tonight. Why not come back next week or later this week and say what the Government is doing," Mr Kelly told the Dáil.
"The Cabinet sub-committee on Covid, with (chief medical officer) Dr (Tony) Holohan and Nphet (National Public Health Emergency Team) is tonight.
"After that - the Government should make the decisions.
"Why have a Taoiseach and (a) minister on radio, a minister on the television and two live-streamed parliamentary party meetings all making reference to preparing for the first of March?
"Everyone is hanging on everyone's words."
Earlier on Thursday, Mr Martin told Live95 Limerick radio show: "We will be reopening schools on a phased basis.
"Nphet will be making a presentation to us (today).
"The public health authorities want to do this on a gradual basis because they want to monitor the impact of increased mobilisation of people on the spread of the disease.
"Too many people coming back at the one time is just not possible because of the impact, given the nature of the variant that we now have, which is highly transmissible and more dangerous."
Mr Martin said the Cabinet sub-committee will today make a definitive decision on the return of junior and senior infants, as well as first and second class pupils to school.
He said the recommendation will be brought to Cabinet when it meets next week and an announcement will follow thereafter.
Mr Martin also said that the first phase of reopening schools will be monitored by public health officials for two weeks before further classes return.
"We want to roll out the vaccines and get as many people vaccinated as possible, that will drive down the spread.
"We have already seen in the nursing home settings and hospital settings that the outbreaks are reducing, the number of people getting the disease is reducing as a result of the first vaccine being administered.
"That does give us hope and it does give us a sense that if we are very cautious - we can keep the trajectory of the virus down."