The Taoiseach says there could be a “spillover” of Delta variant cases from Britain.
A range of COVID-19 restrictions are due to be eased in England from July 19th.
However, experts are concerned the more transmissible Delta strain could spread rapidly through people who still aren’t vaccinated.
Micheál Martin says he's worried this could impact Ireland, pointing to the recent rise in cases in Scotland and England.
He said: “At the moment, hospitals are very busy across the country - the view is many people who may have postponed elective procedures or diagnostics are availing of the service.
“We want to restore non-COVID health services - the Delta variant could damage that in time, if the volume of cases goes very high. And they will go higher in the coming days at week.”
“When I spoke to the Scottish first minister, she was very clear to me the degree the Delta variant - to use her phrase - rips through the unvaccinated population.”
He said it’s still important to prevent people from getting COVID-19, and a ‘very laissez-faire’ attitude to the virus can accelerate its spread.
He added that long COVID is a very serious condition, and there’s still work to be done to analyse the long-term impact of COVID on health services.
Talks are continuing in a bid to allow indoor dining to resume in pubs and restaurants in the coming weeks, along with other indoor activities.
Mr Martin said the caution around reopening is to protect the "gains we have made" in the fight against the virus.
The Taoiseach - who received his second dose of a COVID-19 vaccine today - was speaking as Ireland recorded its highest number of daily coronavirus cases since April.
More than 70% of cases are now being attributed to the more transmissible Delta variant.
